Roof Ice Dams and Snow Loads on Structures

Added: 2026-05-16

[00:00:00]five four three all right good afternoon everybody good morning uh my name is Scott Hamel and I am both the host and the presenter this week which I don't know has that ever happened before actually but um they said can you be the host too and I said sure so um so this week's uh sort of late ad to our semester schedule is um a presentation on roofs ice dams uh originally envisioned to be also in some discussion about snow loads um but uh we may not get to that because as we put this together we started realizing there's kind of a lot to talk about with just ice dams so um that might have to be another presentation so um presenting with me today though not on the original schedule which is my fault um is Dr Bart Quimby um and uh so in the way of we didn't do introduction slides but in the way of introductions uh I am a professor of civil engineering here at UAA um in the area of structures uh and Dr Quimby is my predecessor um in the same job actually so um so that's kind of neat I think this is actually the first time we've ever done a presentation together sure thank you so that's kind of cool too so historic things are happening um and I also think that I might be the only one with the predecessor all of our long-standing faculty have not been replaced so um all right so I'm going to start off here's a quick outline we're going to talk a lot of a little bit about heat transfer I'll try not to I'm not a mechanical engineer I don't have a degree a PhD in thermodynamics so that means that you will be able to understand what I'm saying um hopefully uh and so we'll talk about that and then um Dr Quimby will talk a little bit more about how and I'll talk about what happens and why you get ice damming what happens on our roofs and then uh Dr brimby Who has a lot more experience than I do sort of poking at these things and talking to people and living in Anchorage a lot longer than I have um we'll talk about what to do about them um and some case studies and like I said we probably won't have time to get to my short discussion on snowboards um uh as a disclaimer uh for this presentation uh I wanted to just one of the reasons that I pulled this together is because a lot of people are asking questions about it a lot of people were talking about it there's a lot of misinformation out there there's not uh super great website that explains it um and so I am not an expert in this area and so hopefully I wanted there to be a venue for a conversation um so the YouTube uh chat is open so feel free to ask questions and put in comments um in there or we'll try to leave some question time at the end because really you know the idea here was to kind of pull together Engineers Architects contractors homeowners and just sort of spread the knowledge and also provide a reporting uh which people can look back on this so all right so you have to agree all right so uh uh there are three ways that heat transfers from one object to another um radiation convection and conduction right and so uh radiation is has involves electromagnetic waves um the transfer basically from a hot body to a cold one if you go looking up radiation there's a lot of talk about black body radiation um the idea being that if you have a perfect quote black body um that it will either absorb or emit 100 of its energy um you know in or out depending on whether it's hotter or colder than surroundings and those of course don't exist in real life but there are some substances are close um I actually did a little bit of a giant Deep dive uh you know one of those like internet rabbit holes on this um and because what I was trying to find out is and do some math on actually how much uh radiation how much radiation goes from a warm house to a cold attic and I didn't get a good answer um what I got a lot of is if you live in a hot climate there's a lot of radiation that comes from the Sun that warms up your shingles and then permeates into your house and there are ways you can put in reflective things to stop that radiation if you live in a cult if you live in a hot climate we don't live in a hot climate and so it appears there's very little um at least easily available information about the other direction and so for the purposes of this presentation I'm going to generally ignore radiation we know that it happens because if you in one of the versions of infrared of radiation is infrared so if you take a infrared picture of your house you can see heat coming out right so we know radiation happens um but by and large I think it's a minor part of the actual movement of heat from your house uh to your attic or to your snow um so that's number one uh convection is the transfer of heat from one object to another due to the movement of fluid in this case air right and so this actually involves the molecules moving from One Direction one place to another essentially the the cold the hot object heats the air the air moves and thereby the energy goes somewhere else right and so I'm not uh convection is not a huge uh movement of heat in the wrong direction I don't know if I'm saying that right but um I'll talk we'll talk about connection more um convection sorry more as we go but for the most part the convection that we're going to talk about is convection that we're trying to to trying to move heat and one of the ways that we can move heat if we want to move heat is convection um it's it's not a mechanism of heat loss I guess is the best way to say it it is but it's it's uh more minor than the number three the big dog in room is production right and so conduction is where heat is transferred um basically from the hot end of an object to the cold end or from one object to another by touch right so the idea here is that the molecules are moving fast and they actually are touching something else and they bump into the other molecules um and heat up the other substance or move along from one end of an object to another um and the an ability of the an object's ability to um conduct heat is thermal conductivity so I'll talk a little bit about thermal conductivity but the idea is you know we have insulated materials they prevent thermal conduction they have low thermal conductivity you have things like metal which is high thermal conductivity and it allows heat to move through it very easily right so um so those are the basic concepts of those three the the fourth thing that I basic concept which I think is worth reviewing which most Alaska would probably have a good idea if it's a stack effect um the idea with the stack effect is that essentially hot air rises right and so we have uh warm air which is it turns out that warm air has a lower density than hot than cold air and so uh you know just like a balloon underwater it's going to move upward right and so warm air is buoyant and so it will move upwards and in our houses that has the effect that um you know if you have a point source like a chimney uh or a fireplace then that heats up the air then that buoyant air moves upward out the chimney it can't go anywhere else right because it's in a chimney um but that creates a low pressure area around the warm air which causes suction um and so then all that air has to come in from from outside it comes through cracks it comes through doors it comes your windows but it's going to generally come in near the bottom of the house and work its way up the stack effect is most pronounced in chimneys um and vents but it also happens just in the house itself right because the house is warm and the attic is potentially cold and so air is going to move upward so um so that's an important concept of some of the stuff that I want to talk about um okay so some more conduct going back to conduction right the the third and most prominent uh movement of heat out of our houses um so as I mentioned there's thermal conductivity um which is expressed oftentimes in you is is conduction is uh uh or k sometimes the thermal conductivity of an object is a small K but you'll see it if you start looking into housing and things of things related to housing um sometimes it's it's given as the the variable U um and that it in uh SI units is watts per meter Kelvin um I I actually get a little bit annoyed with you uh some people use you it is essentially if you move down further the inverse of the r we're all familiar or potentially uh you've heard of r value right most construction materials are rated in terms of their r value so those are just inverse of each other so if you see you you just inverse it and you have the r um essentially one is how much U is how much heat will pass through and R is how much you're stopping to eat right the higher r value is is less conduction of heat so better insulator a higher U value means better conductor of heat um so I'm going to stick with r value for the rest of this but just so you know in case you're you know Googling some stuff and you see you that's what it is also important to note is the units of this stuff uh there is the both the s i and the um uh Imperial versions of R the r values that you see rated for construction materials in in the United States is the lower um one which is feet squared hour for degree Fair degrees Fahrenheit per BTU which doesn't entirely jive with the SI because watts and etus are not equivalent so that's why there's a power in there but in general R is given as a function of either you're talking about the whole r value which is uh basically everything other than the over inches or you're talking about the R value per H right so it should be specified typically you know foam insulation is usually given as r value per inch but generally you might talk about a wall as having a particular r value um the good news is I'm going to do a lot of the math for you uh in this presentation and so you don't have to worry too much about that you should be aware that there are a few different units of R and the numbers are completely different like any other unit right so if you get stuck in things that don't look right um all right uh so uh one last piece of conduction Basics is that the temperature gradient across uh a wall or an attics or a roof or a window um is a function of the different R values and densities of R values as you go across and so you can kind of see that there in my little um My Little ceiling right you have 5 8 of an inch of Chip wall board uh I think I have five and a half inches or I can't remember where I put something something on the order of five and a half inches of fiberglass that insulation um some OSB and then maybe you stuck two inches of extruded polystyrene on the roof and what you see is the temperature gradient will sort of you know be steeper um across things that conduct well right so the OSB has a kind of steep line because essentially the temperature on the inside of the OSB is going to do the same temperature and if you have better insulating materials like polyurethane or extruded polystyrene which insulate better than uh per inch than things like fiberglass and cellulose then you'll have flatter lines right and so this becomes important in not so much what we'll talk about today except a little bit um but uh so some examples of this are for example um you know the windows in my uh my old house uh if we close the curtains uh and we get a lot of ice on the Windows right and this is because uh there was there was this much air you know there was there was four or five inches of air between the heavy curtains and the window but the windows had such a low R value um that the temperature gradient through the air was actually flatter than through the window thus the freezing line the 32 degree line which called isotherm or that it's really a plane right that freedom plane was inside the house right so that's why we got all that ice on the inside of the windows and then there's condensation other reasons for that but um so you get this all over your house and if you live in Alaska you've seen this a lot um but the the important thing that I want to point out is the 32 degree line right and that 32 degree line is going to be straight across in this instance but depending on what your house looks like it may be up or down uh you know if you have an area of a lot of insulation if you have an attic fan that that freezing line might move down um because you're heating you know the area and it might or it might bump up and go uh you know like my example of the window is that the freezing line actually bumps down and goes into the house right so therefore the air inside the house some of the air inside the house is freezing and then it'll bump back up so you think of your house or your structure it's got an envelope somewhere completely surrounding that envelope is a blanket um that is the 32 degree line right so we're really concerned with that 32 degree line and you have to think about both the insulation but also the thing that I've glossed over which is convection right so if you have weeks of air or hot air moving out of your house then that's going to affect your lines okay uh now the last piece of concept here like I said at the Times um is uh what is the insulation value of snow right turns out that snow is a pretty good insulator um and so I went digging and found this fantastic article from 2011 on the thermal conductivity of snow um now if you look closely at this the y-axis is in the is in thermal conductivity so that's the the metric version of uh in watts per meter Kelvin and the density is in kilograms per meter cubed and I know you can all easily translate that in your head to the densities that we use in this country so I did that for you um and I converted it to r value per inch and density in pounds per cubic foot right and so um and and this one in my head at least makes a lot more sense because if you think about snow um when it's super light and fluffy right it's mostly air and air is a pretty good insulator it turns out that the R value per inch of air is in the neighborhood of about three and a half um and I didn't so really this graph should probably it doesn't go to Infinity right it probably curves over and sort of heads towards zero at about three and a half to four um but I didn't really bother with that because that's that's like this area down here and there's not really any data and we don't really care right so um but in in general it makes sense because it should when it gets to really like fluffy snow which is about five pounds per cubic foot um it'll it'll probably curve over and over here so but more importantly it's the other side of the graph when we get to more dense air snow um in the neighborhood of 15 to 20 pounds per cubic foot um it comes down here to about one and sort of leveled off ish 2.5 so so kind of remember those numbers right we have two is is sort of medium fluffy so um 15 to 20 is pretty pretty dense snow um the the snow that we got in December uh I believe we measured uh in the neighborhood of anywhere from about six to ten uh pounds per cubic foot right it was pretty fluffy when it first fell so it was probably it was a lot of air so it's probably way up here in this in this two to three hours per inch range and then of course as it settles right and sinks and becomes less um one of the one of the things that was sort of interesting to watch psychologically from the structural engineering community in both December and then the other big storm in January was people freaking out because their roofs looked like there was a ton of snow on them um and that was one of the reasons for that was because the snow densities were some of the snow densities were in the six to ten thousand cubic foot range right so we had four feet of snow on our roof but it only weighed about 25 pounds per cubic per square foot which is way below design um for an Anchorage roof and so it wasn't really dangerous but people looked at it and they were like wow there's a ton of snow um there's four feet of snow on my roof right but over and then three weeks later we hadn't actually gotten any more snow but it all settled down to the more so the higher densities and everyone was like oh we're good you're like no there's the same amount of snow right um anyway so there's an element of psychology involved there but um so this is this is kind of a cool figure um for that um and and as you know we go forward in years now and I there's I know some colleagues in town do some snow measuring it'd be kind of fun to point uh you know to put some data points on here of like you know snowstorm do you remember right like the two ones in December where what range were they in here okay uh so this is my attic example of what is what what does that mean when you put some snow on your roof right um and this is this goes back to I didn't draw the line but this goes back to um that uh this basically this concept right as you have different insulated materials then your your temperature gradient changes and and as you go through the attic and so for the purposes of this we're going to assume a completely sealed at it right this is not true but we're going to assume a completely sealed attic so there's a layer of air basically between your ceiling and your roof right um your your insulation is above your ceiling which is pretty typical um in Anchorage and so you've got your ceiling insulation your air insulation your attic is actually a layer of insulation um if it's completely still air and then your snow which is also insulation right like we just talked about so my first example if it's cold outside uh zero degrees and we have a 24 inch attic then the bottom of the snow which is what we care about here is 20 degrees so everybody's good right you have no melting of our snap uh if you have a low slope roof and you're near the uh the flatter Parts particularly near the eaves and you only have 12 inches but and you have more snow uh right 36 inches at R2 so that's that that sort of uh six yeah uh 10. yeah 10 pounds a cubic foot um which is completely reasonable for like December what we got in December uh already the bottom of your snow is at 32 degrees right so and it's cold right it's zero degrees outside so um so that that right there shows you the differences between a higher slope roof and a lower slope group than how much snow you get uh if we keep with this example and we take the same two addicts and we increase the temperature outside to 20. now your left attic uh still still with some fluffy 24 inches of fluffy snow is is now above freezing at the bottom um and the one on the right uh same same scenario is at 42 degrees right so so now your snow is heavily melted right um and um so here's an example of what is unfortunately somewhat common in Anchorage which is uh probably like a cathedral ceiling um or some some other construction where there's a very small air space only four inches of air space and here we have the same set of scenarios 20 degrees 24 inches of snow um and now we're at 41 degrees at the bottom of the snow and the same scenario except for 36 we're at 45 degrees right so reducing that air space even again this is a sealed airspace right no no air movement at all just reducing the airspace gives you gives you much warmer snow um and then so what's going to happen well it's going to mount right the bottom of your snow there's going to be a temperature gradient across your snow so the bottom of your snow is going to start to melt you have a slope Groove that means it's going to uh the waters would go somewhere right we'll talk about that in a little bit but it's going to melt the snow is going to densify and then you're going to end up with this right so the snow is going to identify I lowered the R value because the snow densifies I reduce the amount of snow basically I reduce the amount of snow and change the R value until I got to 32 degrees right so this is sort of the what happens right and it is that you know you're gonna get water uh things are gonna melt and condense and densify and until you get to a point where it freezes again right and so that might be depending on your the r values and stuff that might be uh you know 14 inches of snow um over here when it's zero outside it's 30 inches of snow right so the outside uh outdoor temperature has an effect in on that as well um here is a poorly insulated house uh with people that like it to be hot uh so I increased the indoor temperature to 78 degrees from 68 degrees which I've totally seen in is wild um but uh my parents who don't live in Alaska that's about right um uh so if you have a poorly insulated house and you increase your temperature then even with 48 inches of snow and a nice big attic you still have 32 degrees these on the bottom side right and if you increase your outside temperature you've got a lot of melting right and so that's probably enough of those all right so lots of other factors that I haven't talked about right we have chimneys that are poking through this attic space that are adding heat um we have bath and fans and plumbing vents we have envelope penetrations themselves right there's you're not going to get a perfect fit around your uh your bathroom fan right so you're going to actually get convection through all those Utilities in addition to A reduced amount of insulation over the attic fan or the bathroom pan etc etc etc right so I didn't mention step groups right if you have a whole bunch of walls that are going up and down as your roofs go around then you've got heat coming from the wall potentially um very complicated system but the basics of you know how much heat do I have how much coal do I have and how much insulation do I have um that's kind of the basics so all right and then uh oftentimes many people have heard uh the terms cold roof and hot roof and so here's the horrible definition the cold roof stays at the ambient temperature and so the idea here is everything I just talked about in terms of um conduction occurs right no matter how much insulation you put but it didn't give you um an r60 or an r80 roof which exists right but basically the same stuff happens it just happens slower right you're still going to have heat going through no matter how much insulation you put on and so you have to get rid of that heat and with a cold room you use convection um to get rid of that heat right so you have to have a positive flow of air um which uh Bart will talk a little more about but you have to have a positive flow of air to remove that heat in some shape some way right and then then you have a cold roof because then your snow stays Frozen and you don't end up with that water problem um here are some designs of you know sort of normal and again we're we're implementing the stack effect here right we have heat and cold above and so the air will naturally kind of get sucked through as long as you don't go and blow a bunch of insulation into this spot right or uh if your roof vent if you don't have events and your roof vents are completely plugged with snow then and you have a problem right so you can you can foresee a bunch of stuff that it will not go right um here's an example of some cold roofs that work these are Bart's photos actually um and he'll talk more about the eaves melting um first and why that happens but that's an indication of cold roofs and then uh the opposite of that of course is the hot roof right the idea is that you have no insulation um and no concerned thank you no convection right you have you have hopefully you have insulation right uh you might have no insulation right yeah that would be a very hot group and um and so basically you get what I described before which is um heat uh you know the bottom of the snow is over 32 degrees and so then then you get melting and um and your isotherm uh or line or Surface is is up inside the snow right it's basically if you go back and look I didn't mention that but in this previous one oops not that one what are you doing there we go this one this black line here is the is the isotherm right that's the 32 degree line so you have to you know often you have to think about your details where your wall meets your roof or things like that which is a whole other presentation um but in this case the that line moves up above um and what you'll notice of course is that the water flows down until it hits that line and then it freezes right and so you've got this uh this classic ice damming effect where the Eve is cold um and then the uh the the line here crosses through that ice and then you have a little a little Lake of water up here um and the interesting thing about this is that the water stays water right because this isotherm is a constant thing of course this is a dynamic system you might get water streaming across the top it might get you know changes in temperature outside you get more melting of snow but the water's there like it's not going anywhere right and so um and I think on the next slide we talk a little bit about well this is what I just said right um and this is a picture uh is this your house pre prefix prefix where the water actually leaked down this is a cool picture right because the water actually leaks down the wall and froze because um big huge icicles the ice damming is happening and the roof is failing and and allowing that water to leak through that that location um and so more on that later yeah um so that's what's happening um and so one of the things some people say well you know is so is it is a hot roof bad well maybe maybe not right and so you can decide to have a hot roof um I actually I didn't take a picture of it I saw a hot roof um it was actually out in the valley about a couple of weeks ago and it didn't have any icicles on it um and it was because it had really it was um insulation went all the way to the tip of the eve and Eaves were really short um they were only about four or five inches maybe and so the water was based and there and it was only about three inches of snow on it um and this is like February so maybe six but the snow was melting right like there was there was there was only this much snow on the roof um but there was no icicles because the e was so short and the heat from the building was kind of migrating through the foam there's a foam roof out to the end and so there was there was no ice so it you know if you're careful and that's what you want then you can make a hot roof and it'd be okay these are the problems right you need to have you might get bikes uh you might get cool icicles right uh but you need to make sure your eaves can support that load um you need to make sure that that pool of water isn't going to get into your OSB or your your roofing material you know you need ice Shield basically a waterproof roof up a certain height Etc so you just need to know it's a hot roof here's some great examples of hot roofs it's kind of fun once you understand all this you can kind of walk around town and just look at them Bart's going to show you a bunch of examples of hot roofs versus cold Brews here's an example of a hot roof that or a cold roof that isn't right so you can see in the cert in the yellow circle there um there's supposed to be event but it's not doing its job right either the the slope is too low or the you know the eve vents are plugged where there isn't a big enough height difference between the two to get a good stack effect or whatever they stop working right and it's very obvious that it's not working um I think I already kind of hit most of these right we understand that more depth and higher insulated snow is gonna is gonna cause your your freezing line to move upward um uh cold temperatures in some in some ways the cold temperatures actually help because it keeps the snow cold um but in other in other ways it causes the ice damming itself to be worse right because once that water is moving as soon as it comes out uh either what we call daylight it's going to freeze right um and so some some that's happened a bit this winter um and you've seen more and less flow because of the temperatures um uh the other thing that I don't I didn't actually put um in here so this is my uh I already said most of this right is it if you're going to have a hot Roof then make sure you you know design for it essentially um I want to leave enough time for the barge talk but um uh the other the other thing I was going to say actually let me back up for a second um so one of the reasons that we've had such a problem with this this winter um I alluded to it this is my own speculation um is I alluded to the temp the the snow part right we had we had a lot of snow it was very insulative um and not only does the the snow add to the insulation it also adds to the volume right because once you get melting under the bottom there's just a ton of water coming off uh the other thing that happened um which I haven't heard too many other people talk about I want to go back to my whole group uh or actually no I'll go back hi Stan um is that we had a period in the end of January where this the temperature got up to 42 degrees for a couple of days um and and then after the two days of 42 degrees it actually sat at about 29 degrees for about a week and so what happens with a cold roof is that uh if if your attic is at 42 degrees you're you're not you're you're not going to get a lot of you're going to get melted right your cold roof becomes a hot roof when your attic is at 42 degrees right and so um irregardless of how much insulation and convection you have right in fact in this case your convection is actually hurting you right because you're sucking in the warm air that's outside and if you live in a super Shady spot where you don't you know or a low you know you live by Campbell Creek Science Center which is always colder than the rest of town and you know your house is colder then maybe you're okay right so so that happened and all this all the roof swarmed up and then it and then it didn't hold that it didn't cool down very fast it stayed at about 30 degrees for a week and so melting continued um some of those addicts probably held that 42 degrees um and so that's one of the reasons why people have never that's what my speculation of one of the reasons why people who have never seen ice damming on their houses before so I right we had all this snow and then we had this warm up so um that's you know kind of potentially what happened um okay I want to skip that and um and turning it turn it over to our current place um yeah I got a call from Scott on Wednesday saying oh I'm giving this presentation have you heard about it and I said yeah so if I'm using your slides you want to come help with it here we are um yeah he's done a great job of explaining a lot of things um and I'm going to just tell stories probably so that's how you work itself so um with bands you can live with it and that's an option um you can attack the symptom and deal with it that way or you could turn the roots into a cold roof which is a long-term solution right up there and live with it but uh sometimes it's really the only affordable solution is is to just figure out how to deal with it so what the way you deal with it is you make sure that your roof membrane is such that when you build the ice dams the water doesn't get up under the shingles head into the house if uh and you make sure that your E's are strong enough to hold the snow though I've never had a problem yet where I've seen whether these haven't been strong enough to hold the ice usually they're you have plenty of capacity structurally so that's not a problem one of the problems that may exist is how do you keep the ice from falling on people and things you don't want it to and usually that's a roof configuration problem more than anything else one of the pictures that we had back here was my mom's house and the entryway used to get ice you can see icicles off on one side of the roof there would fall you'd have to walk underneath all that and the ice would get it so once when you're doing some remodeling we added we changed the roof structure to redevert the water so it doesn't go over where people go in and out of the house and and also that ice used to build up on the walkway and it was a little Hazard so there are some things that you can do architecturally to kind of change that problem so um a lot of people are asking right now what can I do I've had all these problems this winter what can I do to prevent it in the future and so we'll kind of talk a little bit about these things um and if you're going to change it then there are some requirements um first of all there is a structural requirement to make sure that if you have icing in your area that they actually double the snow load over the eaves and you're designed to make sure that the eaves can handle that um and you can retrofitting that might be kind of tough but you can do that um let's attack the symptom here a little bit I found a lot of phone calls this winter about Ruth and problems that people are having having right now and how to deal with it because it's raining inside their houses and all these fun things are happening which had never happened before in the 40 years or whatever that they've lived house um there are some things you can do to try and um take care of the ice dams you can follow them with heat tape and you see this occasionally just drive around town all the zigzags at the heat tape on there and that will create paths through your ice bands the water go through you have to be careful a little bit about that um one thing that I recommend with people it's kind of late to add that in the middle of the problem uh the other thing I didn't put in here is suggest that you just get rid of the water source so that'll shovel your roof and you don't just shovel it at the dam you have to shovel all the way up the roof because that's your water source that's going to be coming down the hill one thing people see if they shuttle part way up the roof is they're cold roofs now are cold right up to there and they create new eye stamps right where they had shoveled too so you need to get rid of all the water uphill so you'll never have an ice standing problem if you don't have snow on your roof all right so if you also don't uh don't shovel your roof onto another part of your work oh yeah there are some instances of that and you can cause your room to collapse um yeah yeah shovel it off shovel it off uh there's some strategies and most of them involved for people who are younger and fitter than I am to make sure that they get done um but uh we've had friends fall off roots and all sorts of fun things and so our son the ER back gets to see those right anyways uh but anyways um to deal with the symptom you need to either thaw the eye scams or get rid of and that's really your Solutions at this particular time when things are building up uh hot roofs are really nice because they do snow removal for you right they melt it all and it all goes down to where um it refreezes um but so you probably don't have as much to shovel as if somebody has a cold roof uh the other thing making a um a roof a cold roof is kind of a long-term solution and you're probably not going to do it in the middle of the problem you're going to do it in the summer time or sometime when it's easier to do that and if you remember Scott's slides the best thing you can do is remove the heat somewhere between the insulation and the bottom of the roof surface so convection is generally the way we're going to do that we need to pull the air out of there there's a number of strategies that you can do to do that um another problem seal the vapor barrier is actually more of a problem with spring thaw if you have bad Vapor Barrier you get ice inside the roof and it comes down in the spring so oftentimes through light fixtures and other places uh if you look at his mathematical models increasing the insulation will also um make it so you have less heat to pull out of the Roof System but it won't eliminate it but the biggest thing you want to do is increase the ventilation and I need to do that correctly so let's talk about this story so um I'm real proud of my house I've built it started building it in 1983 and we're still doing it um how didn't you get you whoever um but I have never had a real icicle on my house ever right so when I when I um went to uh re-roof it a number of years ago I didn't bother a nice Shield I said boy I've got 30 years of experience with no ice spamming so I don't need it so and we have no building oversight Amigo River so I can do whatever I want and so I I did that well the other thing we did is uh we had one story garage and um that he pipe that came out of the garage was up in the roof far away from the edge well we raised the roof inserted to the second floor moved the Heat Outlet right up against the wall and thought everything was really nice until that winter and I noticed all these icicles forming realizing that well I had a really nice cold roof in this one location I had a whole lot of heat and so how do we deal with that well we could get rid of the snow in this case I don't need to shovel the whole roof just over the influence of the heat source and uh but it was really cool from from uh a professor's standpoint yeah here we go if you look here the edge of the ice followed this curve right here of the isocline and I had a nice pool of water right there and uh it was the bottom of that ice was curved just like I expected it being in the picture right there which is really I was excited about that um but we ended up shoveling and next summer uh decided to go in and deal with the problem and one way we decided to deal in this case was to build a very ventilated chimney box around it to take the heat from it that pipe out as soon as possible we also cut great big holes in the roof underneath that so all the heat from the roof space goes up and through probably you shouldn't have put the dent in the bottom because I have plenty of events and everything that's going there but as you can see from the picture on the left you see a little bit of ice damming in there you're going to get some of that on almost every roof just because when it warms up to 42 degrees and you get all these things are happening you get a little bit of ice sometimes on the end of the e but it's nothing like the dam that was there before and this has been functioning real well for about 15 years and so I'm pretty happy with it all right um this picture didn't turn out very well but uh you know I added ventilated space so I have this through this picture um so this is actually to solve the opposite problem which is heat there's a little house that we have in Arizona and I had a lot of problems with heat and other things needed to be re-roofed I tried to hire a roofer to do what I'm doing here and they say we don't do it like that in Arizona um that's fine so I just did it myself but what I ended up doing in this case put a metal roof on and I didn't have to put a new diaphragm down I just raised up and put some stringers across the roof to put the little roof on and a ton of holes were placed uh on the eaves down here and a ridge vent on the top and then the building official came by and wanted me to put holes all over the roof so I did that too to get the uh the attic space and um it reduced the heat in the house empirically from 15 to 20 degrees over what it was in in the uh summertime and of course they don't do it like that in Arizona but you can do this in Alaska for the same reason that is to pull the heat out of the attic space and vent it somewhere else here we talked about having that space in there and I've got a friend of mine with a real icing problem I've been trying to get in front of this for years and so far I haven't convinced him but um uh so anyways uh the idea is you can go back and add ventilated space even if you have a cathedral ceiling you've got some other things going on just basically build a roof over a roof and this is actually the building official wanted me to show that the added weight of this new roof was gonna help out I kind of laughed at him because we took two layers of shingles off of that roof and replaced it with a metal roof which was infinitely lighter and so we got past that one pretty quick but it works um so the idea is you want to increase the ventilation and also some of these roofs that are kind of flat um you end up with not a lot of vertical space between where the air comes in and where it goes out and so you can add chimney type cupola things on your roof that will increase that height and increase the airflow that you go through there so I had a friend of mine who Eagle River back in the 80s it was complaining about his old house had always had all this ice in a very little slope to it I suggested he'd do something like this and he went off and did thought about it and next winter he comes to me and says it really worked I said oh you did it and he goes yeah I put six of those things on my little house so you know you get enough of them you know it'll ventilate that it works really great but the part of the idea here is to increase the airflow through the system and if you can increase the height between where the air comes in and where it goes out you're going to increase that airflow and it's going to take more heat up as you go so I just went on the on the net and look for things and these are from hot climate areas but roof fence are not a new thing they use them to remove heat everywhere I mean even old barns used to put these uh kupas on the top of them just to keep them cool inside and it's the same idea you could build one of those on a house in Eagle River and that's really cool I don't know about the anchor chance like it but there you go you can remember just that kind of place so hot roof cold roof is all about design these two pictures were taken about a minute apart on neighboring houses one's hot roof one's cold roof same environment same exposure so same everything um but you can do that what you can tell hot roofs in particular because you'll notice it's it's fine over the house over the garage in this case and you can see every single truss which has a little bit more insulation than you know speed and the snow doesn't melt over the East just melt meat melts over the hot part um in the what you'll find in cold roofs is that the melting when it does take place is actually going to happen over the eaves first and over the house second so you're gonna see um these things happen these were taken just last month just wandering around town hot roofs are are particularly hard on rain gutters which are I'm never really a fan of rain gutters up here because of this particular problem see the rain gutter this is up in Government Hill so after Scott called me on Wednesday it says you know I'm retired I can do it I got a lot of time on my hands so I took my drones I do photography as my retirement Hobby and somebody talked me into a drone lately I just flew it around my neighborhood just looking at everybody's roofs so I can fly my drone wherever I want and this time of year everybody's inside so they don't know so this is my neighbor across the street she has an unheated garage uh in the front of the house and we were there when they built it I don't know how to write this here we go nope here we go uh this pointer is lousy anyway so this is the cold roof and uh you'll notice we've had some warming and stuff over the last week or so and so it's melting around the East it's really great she had huge icicles in front of her door she lives on the left side and uh she might have shoveled a lot of this but her tenant on the other side didn't shovel anything and you you talked about infrared to see where the heat loss is you don't have to worry about infrared up here to figure out where your heat loss is you just get your drone up and look down on the roof and you can see you can see what the problems are and so uh obviously um she doesn't spend a lot of time I guess upstairs and her upstairs and probably keeps it cool but her Kenneth does and it keeps it really and they've lost a lot of snow here and all that snow has come down and froze in the nightstands all over the edges of this and same with uh the other things there so there's a place where we're having heat loss and the heat makes sense because most of the Heat's going to be higher in the attic space and so that's where it's going to start the other thing you'll notice on the eaves there's still snow on the eaves all right because that's cold and it's not melting so we've got the eaves with some snow going on um so there's another neighbor's house great cold roof but he talked about roof penetrations are evil all right because a lot of heat we're going to talk about this and you can see where the roof penetrations are in this year and it's a particular problem most of the time all your melting is the snow right around this and so there's not a lot of water finding its way down you get some and you get some Damien and stuff around here and same with over here but we've had so much snow that we're I'm going to show you like kind of damn that I never expected to see but you can see in their warm roof or cold roof that there are some hot spots where the utilities come through um Ridge pants everybody always asks me about ridge vents don't they get covered with snow and don't they have problems then I guess they do but as near as I can tell they're the first things to melt and there's not a lot of snow around them so that's no probably as our water goes down it freezes before long before it gets to the east so I imagine that there's a little bit of ice underneath the snow there so if you're up on your roof shoveling be aware of that it could be kind of hazardous but once they open up uh they do quite well these houses have Great Southern Exposure and so what we see around the eaves of these houses is some melting going on over the eaves already now that spring is starting to spring on us here and so uh the roofs have these houses don't have particularizing problems uh but they do have places where heat is escaping from the houses um all right this is an older home in the neighborhood and they have a few uh apartments in and around it um in the Arctic engineering course which some of these slides came from that I did quite a long time ago um we show this house on the left a really steep roof it has slab Avalanches every year which is really cool um right over the entryway so they've built a little roof over the entryway to get hurt and you can tell where the unteated carport is and then the two apartment buildings uh a lot of Heat going on and the snow and ice are still building up on the eaves but the this one was kind of extreme hot roof situation going on um here's a mix they have a they have a heated garage so there's a heat thing over there but they probably don't keep it really all that hot and uh may be well vented but the older part of the house it's definitely a hot roof and then the newer part of the house has a cold roof so you can have some of the same in both the reason why I kicked this picture and they added on to it a couple of times but you can actually see the The Ice Shield that they put on the roof they covered the whole roof with the ice Shield all right and that's great you're not going to have any icing or any water leak problems if you make a membrane like that over your entire roof it's kind of expensive but it's an option um and uh I threw this one in because if you look real close on the ridge they don't have a ridge vent but they put in a whole bunch of little mints all around in here those are not all a utility man some of these are some of these are bathroom Vents and that sort of thing but they've just put those up there instead of a ridge vent um and surely you can see there's some melting along the ridge which is fine they don't have icicles so actually they got a little Sheen of ice underneath their snow but that's another way you know you can add something to your roof that will do that kind of thing so this is my roof um and uh I was smugged online with my friends who were talking about all the water problems they're having I said ah I haven't had water problems in the 38 years we've been in the house and I I built it myself I'm a wonderful guy I'm in tiny cup calls me into the laundry room and says what's all this water falling down the wall and I says I went outside I didn't see any icicles I said I saw a little bit of an ice dam but nothing that that would do that I'm thinking how in the world did that happen you know so I had to eat my words a little bit so I went up on the roof and I noticed around all the the this is a bathroom fan this is a bathroom fan this is a kitchen fan and there's a lot of snow around each one that has melted and all that water had to go somewhere that's a cold roof where does it go it goes just down from the vents and it freezes and creates eye stands a long ways away from the eaves and um so I had this problem with ice dams occurring where I never thought I would ever see them and I think a lot of it has to do with the duration of the long snow that we have here and that that's all ice on my roof that came from those vents up there my solution to that was to shovel to where the snow was no longer melting uh and and I'm getting old I didn't want to shovel my whole roof so I just went to where it was there we have and the rain stopped in the laundry room which is a great thing uh so we'll be reevaluating this possible solution uh don't use these little rooftop vents use something that pops up a little higher it's above the snow and maybe it won't melt all that and insulate it too because that you can see the plumbing band is also melted some snow around but not nearly as much as the fans did so um I don't know maybe I have another summer project going on here hey Scott what do you want to do skip it I want to take some questions okay let's take some questions Scott will answer anything you have to ask so you see if we've got any online because I think we run against our time sorry about that I've got a question about uh like ridge vents at what point does the density of the snow or the depth of the snow block the ventilation um I think as soon as it covers the bench it's going to slow down the ventilation right so I haven't done a real study on this but what do you see from the sides here it doesn't take long for the vents to open themselves up again so you have a you'll have a time after a snowstorm where yeah they're not doing any good Your Roof Systems heating up but what I'm seeing from my little drone experiment here is that these houses who've gone through a heavy snow year with lots of snow ice Damian problems uh the houses don't have ice sanding problems but they're they were able to clear themselves just from the Heat um so there's probably more uh research done on that mine is I don't have any real research on that every time eight years ago I don't do that anymore but the um good question people ask me that all the time and I always have I don't know but when after flying my drone around I'm not feeling too bad about I've had people tell me that it bends through the snow well there's no does have some permeability to it I mean you can't get some air through it but I think your biggest thing is that as it permeates through the snow it's melting the snow and uh it's going to open itself back up again just based on what I've seen in driving around campus I've been looking at this for decades and so I can't drive around town without looking a roofs this time of year it's impossible and all these Ridge Family rooms seem to be doing okay how many accidents [Music] I I actually need to add a picture of my neighbor uh I I was actually looking yesterday um and my neighbor's house is a little bit lower than mine and her and he's got a ridge event that kind of comes out towards my house and there's this perfect arch of snow over the ridgeback uh and then it's vented out to the to the cable right so it's and of course you couldn't see it for a little while until the end melted but it's like basically it arched itself there's so much snow that just you know it melted a little space and then it and then it ended out at the end so I don't know they kind of cleared themselves but um but I still think there's a potential for problems because they're blocked and covered um you know if you think there's there's got to be a scenario in there where the ice starts forming melting and everything going before they clear themselves um not my preferred approach ridge vents um but my anecdotal looking around town flying my drone over my neighbor's houses and stuff like that say in a year that we're having lots of problems the ridge problems don't seem to be significant because every one of those houses that I showed with a ridge fin on there you can drive up to them look there's no ice hanging on the thing there's no ice now uh that whatever's melting there is not going far down the roof before it refreezes but there's not a lot of source snow to create ice damage to the point where it's kind of back up under the shingles either so the other thing we didn't really mention is uh you can add mechanical ventilation um obviously from an electricity standpoint that's not ideal but you know if you have a low slope roof and you don't have a big stack effect um you know you know stack effect is based on both the temperature differential and the height differential between between the low the low Vents and the high vents and so if you have a low slow Groove then it's really hard to get that elevation difference so if you put fans in and you don't even have to run all the time right yeah you can put them on a temperature sensor uh we had one of those on that house in Arizona and after I put the metal roof on it it that fan would run all summer long after we put the metal roof on it with the air space to pull the heat away it doesn't run all that much anymore um a couple of online questions uh how does how does this year snowpack compare to capacity that is not really related what we're talking about kind of um but just because I happen to know so we in terms of load we hit about 90 depending on where you are in town of the design capacity of Bruce and design is a minimum yes no safety Factor above the design yeah depending on how the roof is it's not even built obviously some of our commercial structures had some issues but that had more to do with the materials that it's not so that's a kind of combination between the two yeah not you know some people shovel their roofs for ice standing reasons um some people shovel their roofs because they were nervous about the construction but we didn't actually exceed our roof design loads um but obviously these two things are related right because as I mentioned at the beginning you know the the um from an eye standing standpoint the the four feet of fluffy snow is actually way worse than you know 12 inches of super wet heavy snow but from a structural engineering standpoint potentially you could have more load if you've got a lot of spring rain um and a bunch of late April storms so how one interesting thing right and those questions is uh hot Roots will melt the snow from the bottom up cold roots that melts from the top down so uh what I have seen around my vents and stuff when I didn't I had these Arch faces right you know where the snow melted underneath not the root surface but there's still snow up above so I knew I had a hot problem going on at this targeted places um one question is we have a flat root can we build a well-ventilated metal roof um metal roofs require a minimum slope but you could build one matter of fact the house in Arizona was a fat roof house that somebody built a pitch through over at one point um before we long before we got as a 90 year old house um no it's anybody here a roofer having answered that question but the the metal manufacturer was telling me they don't want to go more than a three I think flattered and the 312 just because they want the water to run off and not cool around the screws and everything else which are all gasket but you don't want to test the gasket that you don't have you know but I think part of our roof in Arizona is flatter than that anyways don't tell the manufacturer so you would have this a little bit to a certain yeah um one other thing on a flat roof building which we didn't talk about the commercial type buildings normally we'll they'll be designed to to slope a minimum a quarter inch per foot so the water drains someplace in cold regions do not drain them discovers scuppers become dams and you end up with pools up there the best matter of fact the best smell removal you can have is heat so if you have flat roof and you go to an internal drain that drain's not going to freeze it's going down through the building right except for the engineering building the old Engineering Building when they first built that they came down and they died in a creek and it just froze at the creek and did it back it backed all the way up to the roof right and there was raining inside the building we had every pipe joint and you go up so you got to worry about that but the nice thing about it and the flat roof that drains to the internal drains and and off you go and see if that's your snow shoveling thanks very much so if you have a subgroup impressive and not live with it because of the load on your roof especially if you live in the house it is maybe not built for the current code well you're not trying to say I have yet to encounter broken Eaves to ice dance and the 40 some odd years that I've been at 48 years I've been here but the uh you know theoretically you could do a structural calculation right to figure out what the what the capacity of your Eve is and then figure how much ice can I put on top of that but you know treat you the density of ice really easy right uh so um most of the time the eaves are at the end of a truss where the top core trust member is designed for what's happening over the building not for what's happening on the heat right so it's probably got more capacity than you than it needs and and typically they're not super long no so I think like eight eight inches starts to be once you get past eight inches of ice on not on the heat that's right or more but the audience of ice is equivalent to the snow load of Anchorage which is 40 pounds square foot right so once you go past that you're in your safety Factor right well kind of except that that code says twice twice the eaves are twice that wall past the E right yeah I mean and that would be worse now that of course assumes that whoever designed the house knew that the code was twice that right uh the problem is is that residential construction doesn't normally get the the structural oversight that's a commercial building bus so it's kind of hard to say this is a really short Eve Building right here but that that ice dam is a foot tall at least you know so you do get you do get some pretty heavy loads but but it's a trap it's a triangle right so but most your weight is out at the end of a cantilever influence lines and all that but um again um I have not yet seen that it's not saying there is any any distressed needs even though you get some pretty big ice dams but you could do a structural Eve and see what you get I think probably the bigger problem is when it when it when they become like if uh you know if you go and shovel it and then it moves up the roof and then shovel it if you have a huge like there are some scenarios I could think of where you next time set up some advice you know not just on the very but those those would be special situations yeah I would highly recommend that if you have an intensity to making big ice fans or you just shovel your roof or you're going to get rid of the source you know it would be probably good to do that not for not for structural reasons but just to minimize the icing problems and you know one of the purposes of this talk today was you know things are melting this is no longer a huge issue like it was a couple of weeks ago I think obviously people are probably still having some water problems um there are some comments that potentially you know as spring happens you might get more water problems as the snow actually melts down um but more so I think it's important for you know people are going to start getting calls um to think about what could and should be done this summer right like where if there's if there's if we're going to be putting an insulation you know adding insulation that blocks the convection is a bad idea right and or is this a one-off year because of the scenario of snow and temperatures that we got and we just had like my house actually has a minor ice dance um which I am not worried about you know because it was a early year and and I I'm gonna suggest that maybe we need to see more couplers that increases your stack effect I mean it puts it as high as you possibly can and you get some ventilation in there yes would you sort of said yes I've seen kind of uh situation other than having like an insulated problem um well the solution that I had for mine that I that I was showing off wherever that was yeah it's back the other way oops you know again the principle is get the heat away from the snow you know how are you going to get the heat away from the snow and in this case I couldn't do it in the roof because I'm at the edge where I only got this much space right and and the stack is just going up through there so what I was attempting to do was to create my own little stack effect right here on the roof in order to pull the heat away from that and I had another picture that I didn't include in here from the Drone shot of of what is happening from above on this and yes there is still a little melting around but just a little I mean just enough to cause maybe this little bit of ice on on the end of the eve but the whole idea was I don't have now those beautiful ice that goes underneath the leaves of my house right I don't like those um but this helps tremendously um and again opening up the roof itself so I cut into the roof diaphragm so that the air from the attic can actually go through here and I made this almost as high as high as the as the hand vents they have on here so that I'm not short circuiting my stack effect right a woman if anything I might want to make it even taller if I was continuing to have a problem because there's a that that heater runs all the time in the wintertime down in the garage and it comes up to the apartment into that and it pretty much solves the problem there you can see that you know yes there's still some heat there but not nearly what was there before and I actually went and talked to uh furnace but a wood stove a company that produces wood stoves and installs wood stoves and I asked him all these questions about if there's any regulations or what kind of pipe they use it's about putting pipe through attics and they were like oh yes we use this insulated pipe and it's like one inch of urethane insulation around height you know which is not enough and that's what I've got here yeah it's and so and there's no no regulations on that there's no nobody has a really hard I can tell or maybe somebody's looked into this but I you know it didn't seem like the folks that were doing this were too thoughtful about it they were very thoughtful about fire you know uh blowing through and about you know ceiling things for weather but the heat part people don't seem to think about it too much so you know adding more insulation uh to to stove pipe through attics and never that's probably a bad thing yeah and probably never a bad thing but I think convections Could That Be Your Biggest friend um okay we're kind of out of time uh there's a few other questions um one of them I can answer pretty quickly uh the question was do we can we reduce the interior room temperature um to lower the basically reduce the melting um and the answer is yes that will help right if your room interior rooms are 50 degrees instead of 75 then that will change things but the the problem will remain right because you're not going to lower it's still zero outside and you know your room is not going to be 35 right so you know shaving off five degrees is it all right okay um thank you you mentioned about um leaks inside um light fixtures yeah is that you said there was a failure of the Vapor Barrier barrier yeah so that's all different yeah we could talk about that for another hour okay um probably a bunch of people waiting for the password for the pdh uh and the it is two words this week uh ice dams with a space all over face ICP space and I think is that the first time we've ever in the space I think so lots of hers here yeah thanks thanks everyone for participating thank you very much [Applause] everyone deciding