SIPS question for the Timber Frame experts

[Jim_Rogers]

At the recent eastern conference of the TF Guild, I heard a talk by a speaker about proper building methods.
One comment that he made was that the heat in the attic during the summer months is directly proportional to the color of the asphalt shingles.

Black or dark makes it hot, white or light makes it cooler.

Jim Rogers

[oklalogdog]

Yeah the light colored shingles making it cooler just makes sense.  Problem is I just don't like the looks of light colored asphalt shingles.  I guess I will go with the shakes and they will surely last my lifetime.  The next owners can do what they want.

[Stephen1]

here is my 2cents worth, A lot windows as mentioned before are not very efficient. As has been discovered radiant heating in the floor is the warmest and most efficient with your type of ceilings, ie cathedral. maybe you should look at changing the heating method. Radiant heat stays close to the floor and does not migrate to the peak to be released by the windows. A lot of work will go into  new and heavier roof, not sure if you have a snow load to worry about there.
Stephen

[beenthere]

Stephen
I think warm heat rises, whether radiant or not .
Put some fans at the peak to gently push the heat down.

[Stephen1]

yes, warm heat rises but because it is radiant, not convection fan forced warm air, it acts differently, it only heats what it radiates onto, thus the warmth stays with about 30-40 inches from the floor. it is an interesting topic, but maybe for another time.

[AvT]

It occured to me today that the simplest installation would be to strip off the old shingles, install some SIPS on top of my exising decking, and then apply roofing on top of the SIPS.

I did somthing similar to my house a couple of years ago but I ripped off the decking before adding insulation because there was an air space between the insulation and the decking.  huge job but no point in installing another layer of insulation with a space between it and the old stuff.  make sure you do it right so condensation is dealt with or you could have a nightmare situation.. i don't know about your area but here up north it can rain in your house when the frozen condensation melts with the sun shining outside.  here the layers MUST be inside vapor barrier then insulation then a vented air space then decking and then shingles.  the air space must be well vented too with no dead air spaces or you can have a horrible soggy moldy mess up there IMHO

[Stephen1]

Some info on Radiant versus Convection heating
http://www.radiantheat.net/how_works_forced_vs_radiant/

[scsmith42]

here is my 2cents worth, A lot windows as mentioned before are not very efficient. As has been discovered radiant heating in the floor is the warmest and most efficient with your type of ceilings, ie cathedral. maybe you should look at changing the heating method. Radiant heat stays close to the floor and does not migrate to the peak to be released by the windows. A lot of work will go into  new and heavier roof, not sure if you have a snow load to worry about there.
Stephen

Stephen, there is minimal snow load here in central North Carolina.  I concur about radiant heating; I installed it when I built my shop and it is truly the most comfortable way to go.

My utilities costs are more associated with air conditioning as opposed to heating, due to our local weather patterns.

[Stephen1]

Not much snow there...just once in a while to make you realize there is a winter.

[Thehardway]

Radiant heats hard objects and bodies, but has little effect on air. Convection heats air but not bodies. This is radiant is more comfortable.  It keeps your feet and body warm but your head cool so it helps you stay cool headed even in the hottest situation

Scott, what kind of floors do you have?  Floors and masonry walls can soak up a lot of daytime solar radiation through the windows and take a long time to cool down.  If this is your situation, adding insulation to the roof will actually make your home hotter and more difficult to cool as the re-radiation has nowhere to escape to.  I have seen this in few cases where people improved insulation and actually saw a rise in their AC bills.  If this is your situation, reflective films on the windows combined with hydronic radiant/convection cooling is the most efficient way to cool things down.  You can forget using conventional air/air based cooling systems in these superheating situations.  You will never win the battle with the sun without using water.  If you have a pond or body of water handy or can do your own excavation work and have some available acreage, geothermal with a water/water/air exchange could cut your ac and heating bills by over 75%. 


I have high ceilings in my house as well. I am just finishing off the drywall in my house this week.  I have 22' ceilings in the in the great room.  There is a 5'X6' window and a 6'X8' glass door with southern exposure in this room.  I am maintaining 60-65 degree temps day and night right now with no heat or cooling in the house.  The roof is 8" EPS sips over timbers with mill finish galvalume.  I have radiant heat in the concrete floors but no need to turn it on as the solar radiation absorption is more than adequate to maintain comfort.  I have found that the most comfortable indoor air temp at head height is 62.  Suprisingly there is little difference in air temps between floor and ceiling at 22'.

Large overhangs at the gable help limit summer heat gain but I will be circulating cold water through the floors in the summer to solve heat issues and using it to pre-heat well water for domestic hot water use. Don;t know if this would work in your situation.
 

[scsmith42]

Bob, the floors upstairs and downstairs are heart pine wood over a plywood subfloor.  The walls are sheetrock.  There is minimal window exposure on the south side of the house, but a huge roof expanse.  The north and east outer walls are pretty much sheltered by trees.

I have a 3-1/2 acre pond under construction about 400' away from the house, and am planning to recirculate water from the deep end (22' deep) to within 100' of the house, so some type of geothermal cooling would be a good possibility.  I'm not sure that I could gain much benefit from heating though, w/o drilling wells.

Most of the house has a cathedral ceiling, but above my bedroom there is an attic space.  Temps at the top of the bedroom in the summer time are usually well above 90 degrees, which is why I'm pretty sure that increased roof insulation will benefit.

[Thehardway]

Good. Just wanted to make sure! Wood floors will hold some heat but nothing like masonry or tile.  Sheetrock likewise if it is painted a light color.  Don't underestimate the pond for heating purposes, with 3.5 AC and 22 feet of depth you might be surprised what it would do.  There is little more required than placing a coil of pipe in the bottom of the pond and making sure it stays there and then trenching back to the house.  The actual geothermal pump itself is relatively inexpensive.