Greenest EVER insulation! (It’s also very cheap!)
– 0 carbon/embodied energy
– easiest installation of all
– comes when most required
– very very DIY friendly
– can be moved around
u guessed it ?
water ….ergg SNOW of course 🙂
I join a picture view from my first floor patio door taken on feb 28 2013 for your enjoyment
( for those southerns that think we don’t have snow in Canada …wait everybody thinks we have tons of it ?? damn .. )
On a more serious note,
i’ve designed my flat roof terrace on my own house to take advantage of the snow we have each year during the coldest phase of our winter in Quebec.
~1600 sq ft of flat ( epdm will be covered with pavers/stones arrangement in future ) ( slow sloped to 2 drains ) roof that has a 42″ high parapet ( will end up being near 70″ total with installation of security glass )
It retains all of the snow that falls in it, and during winter, a large part of it remains shaded.
since the last 3 years, i’ve averaged ~12″ snow cover during December, ~24-36″ janurary and ~24-40″ during february months …
Insulation on top of the steel deck is from R24 to R40 with the EPS sloped boards.
What should i expect to have as total insualtion with let’s say 24″ of snow ?
i know that snow doesn’t have a steady insulation value as it differs from day to day, year to year..
some of it actually melts during hotter day to form an ice sheet under the snow on top of the membrane etc…
What do you think of my idea to use snow on the roofs ?
I plan on using this method on all of my future designs ( unless someone proves it to be worthless )
We’ve had quite of a bit of sub -20C temperatures this winter , more than the usualy 1-2 weeks of the beginning of february.
And i can tell you that the snow made had a serious impact on the heating system load time from beginning of december to the end of it ( wen’t from nil to almost 20″ of snow by Xmas this year .. )
even if the temperatures were very similar ..
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
BTW ... for the record
I really LOVE snow ( not because of the insulation )
Working outside during winter time ( even when it's -20 ..but sunny ) is one of the best feeling in the world ... The quietness of everything, the solar reflections on the snow .. i wouldn't trade
it for southern life in 10 lifetimes !! :) Playing in the snow as kid, now with the kids ...playing hockey outside in the backyard !! :)
GO HABS GO! ( okok ..its now time to go sleep ..stop typing )
Fresh snow has an R-value that ranges from R-0.5 to R-1 per inch. The highest estimate I have ever seen for the R-value of snow is R-2 per inch, but I think snow that insulates that well is rare.
The biggest disadvantage of using snow to insulate your roof is that it increases your chances of ice dam problems. However, if your roof is designed to be ice-dam-proof -- and a low-slope roof with EPDM roofing probably qualifies -- there is no downside to snow.
How would you evaluate snow for calculation purposes then Martin ?
Would using something in the 0.5 to0.75 R value be safe ??
Do you have other examples of designs using snow as insulation on live buildings ??
What about using snow on bottom of side walls with some retaining setup ??
Unfortunately, my roof terrace is @ 40ft height, so it would be very wise to try and move up more snow from the ground. :p
Q. "How would you evaluate snow for calculation purposes then Martin?"
A. As I wrote, snow has an R-value of R-0.5 to R-1 per inch. Fluffier show insulates better than dense snow.
Q. "Would using something in the 0.5 to 0.75 R value be safe?"
A. Yes, that's consistent with what I wrote -- right? I don't know what you mean by "safe," though.
Q. "What about using snow on bottom of side walls with some retaining setup?"
A. Poor people in cold climates have always banked their foundations and lower walls with snow. It's a lot of work, but it's a common approach in rural areas (including Vermont).
Careful Jin, there are some hidden issues with this strategy.
As the snow builds up, the temperature of the lowest layer gets higher and higher until it hits 32F. The water generated there has to drain to an acceptable place before it has a chance to refreeze. An interior drain is about the only way to accomplish that. That sounds like a risky PIA to me.
If you install enough roof insulation to prevent that melting , then the marginal value of the snow's insulation is diminished, so the snow doesn't gain you much. And you STILL have to manage the snowmelt from warm days and direct sunshine somehow.
In snowy parts of Europe, they like to keep the snow up on the roof, but they also vent the decking to keep it cold to prevent ice dams and downspout troubles.
In Summit County, Colorado, they use heat tape on the eaves, gutters and downpouts. That's the worst solution of all.
Sifu Martin :
1- by calculations, i meant more in the complexity of variation of thickness, variation of insulation values ...the complete scheme
maybe approximating the added thermal value would be long and not worth the time ...
2- safe, on the calculation process .. so the results are not exxagerated ( as in safety factor etc.. )
hope i make sense ... please correct my bad use of the terms sifu !
3- yes it involves labor, but hey , its fun to shovel snow and good for your cardio !! .. might not be worth the effort on a super insulated house though
Kevin: good thinking, didn't give this much of a thought ..
in my situation, the roof has 2 drains in the middle of the tapered design, i've been hearing water dripping in the pipes every day above ~ -10c and a little sunny !
And i would never consider snow alone or with limited insulation in any building :p
My current setup was going for R40 at first, but i had to do some modifications and was wrongly suggested by a rep at initial design stage... i would not install/design with anything under R40 for flat roof in my climate.
There are a few weeks usually, where temperature rarely goes higher than -10 and down near -30c everynight locally, ANY additional insualtion ( and with very little add cost ) is a welcomed gift
to help with the head loads.
Interior drains with quality installations are not that risky on EPDM with a clamped/return system.
What kind of problems could arise on a smaller roof with no interior drains ??
Of course, cold decking removes any potential gains from the snow and defeats the purpose.
I also do not consider having structural roof members exposed.
Q. "What kind of problems could arise on a smaller roof with no interior drains?"
A. As I wrote in my first answer: ice dams.
Martin: i don't get it ... ice dams on a flat roof with a membrane ?? what problem does it cause??
i understand the problems of ice dams on a shingle roof with no peel stick etc...regular type roof,
but i fail to see where it poses a problem on a low sloped flat roof with membranes or similar type of waterproofing.
When the ice melts at the roof surface under 24" of snow the water seeks a way off the roof. This melting will happen at night as well, so the water will refreeze instantly when it starts to exit from the warm epdm surface. After a few weeks of this cycling, the ice dam gets large and thick.
At some point this heavy mass of ice will want to slide off the low slope roof. (Remember that the epdm/ice interface turns to slippery water several times per week when the temperatures are right).
This homemade glaciation experiment will tear off any protrusions in the roof deck. If your roof surface is perfectly smooth, then it's just a huge deadly ice cube sliding off.
This scenario is why the Northern Europeans don't use roof snow for insulation. They've studied roof design for 1000 years.
Kevin , thank you for pointing this out.
What is considered a safe slope for ice dams ??
i have 1/8"/ft ...i don't believe there would be any problem with ice movement,
but neway, it will be all covered with pavers/stone ..where the interface will be not that slippery and locked in place ..
what do you think ??
The combination of the pavers and 1/8" per ft. might work.
Keep an eye on those drains though
Kevin, i will try to go on the roof tomorrow and shovel some holes to inspect the current situation at the end of winter.
I have had flat roofs on all of my business ( very slow slope ) and we never experienced any problem related to ice sheets.
Good that you guys pointed it out, i will try and read about the subject specifically for flat roof situations.
But now, my free green insulation is seriously melting away .. the sun is hot hot hot!! :)
Time to tap the maples now ...the sugar gold is flowing like a leaking garden hose connection :)
What about an IRMA (Inverted roof membrane assembly, or PRM - protected membrane roof)? An un- or minimally-insulated roof deck, next membrane, insulation, then pavers / ballast, then snow on top of all this. That way the drainage plane is warm, and water can escape through designed channels and drains. The more snow, the better, no risk of ice dams, and no sliding off.
Curtis: ur idea sounds nice , but defeats the purpose of "additive insulation" .
My goal is to set up flat roofs that already have a high R value, and benefit from additional
free insulation when winter comes.
I have shoveled a ft square of my home roof sunday,
and there is a water layer ( something like 1mm flowing slowly ) because of the mild temperatures of the last few days, and something like 1" of ice under all of the snow
( forgot my cell phone downstairs to snap a picture ... )
I believe there used to be more ice than that at the begining of winter because we had alot of rain and or freezing rain right after the first few snowfall.
The ice is probably what is melting down slowly now ...
but i don't see it causing any problems on this particular situation.
Also, the roof being completly full of snow, there is not much space where something could
"slide" as there is probably an equal part of ice covering all of it.
Didn't have time to invest on searching the web this weekend, will do soon and report findinds.
On the other hand, tasted our own maple syrup for the first time, and it is delicious!! :)
I also boiled my first sap of the season last night. It's always a pleasure to taste the first syrup of the season.
Jin, I'm not sure how an IRMA assembly defeats the purpose? R-40 foam above the membrane, but below the pavers, and an additional R10 or 20 or 30 of snow above the pavers.. Of course you'd want to consider thermal bridging at the drainage gaps...
The warm membrane of an IRMA roof is advantageous, but again, interior drains are required to keep the water flowing. Any conventional exterior downspouts can freeze and clog.
Speaking of flowing water, whenever this melting/draining phenomenon occurs, lots of heat is being sucked out of the roof deck.
How bad is this heat loss?
Since the heat loss equations are all linear, the amount of heat saved due to snow is in direct proportion to the outdoor temperature. When melting occurs, the membrane is at 32F. If it is 70F inside and -3F outside, then the roof assembly is losing half as much heat (35/70=50%) as a snow-free roof.
Assuming an average "snow blanket period" temperature of 17F, then the maximum possible savings of your roof design is (32-17)/70 or 22% of the conventionally calculated heat loss through the roof. This may or may not be worth the risk of ice dams.
You must also consider this: By March or April, all the snow will be melted off. Your design guarantees that a high percentage of the snow was melted by heat from the house.
I think that is one of the lessons from igloo building: An igloo is a lousy house if you want the interior air temperature to be above 32F. But 32F is great compared to the alternatives.
Kevin: one problem in your equation..
when water flows in my situation, it is because we are hitting 0c outside.
or very near it !
The drains go through the interior of the house and into the ground
there must be warm air pushing up through the drains all winter
( some from interior heat, and some from in ground temp )
so that is why i head some water flowing as soon as it gets near 0c
but we've had a few days of 3-5c + the sun hits hard now
so it is only normal that i get a water layer under the snow
as all the snow that is melting on top by the sun/heat is going down through the snow.