thermal bridging

[busted knuckles]

How much heat loss do you think occurrs due to thermal bridging? Is it worth building a wall as pictured? The studs would be about 1ft apart. 2 ft spacing per side, staggered on a 2x6. I am on a tablet, cant copy image link.

http://www.theleapfroghouse.com/index.cfm?fuseaction=cDisplay.learnmore

[UK4X4]

One builder here did the stagered type wall

looks like he moved some of his pics and the links don't work anymore

http://countryplans.com/smf/index.php?topic=8833.0

[flyingvan]

This is a pretty subjective answer, but even on a mild day at work I can turn a thermal imaging camera to the interior side of a wall and 'see' all the studs through heat transfer on a conventionally framed wall

[rick91351]

This is a pretty subjective answer, but even on a mild day at work I can turn a thermal imaging camera to the interior side of a wall and 'see' all the studs through heat transfer on a conventionally framed wall

Have you viewed a 'bridged wall'?  A couple 'green builders'  here are sure not warm and willing anymore.  No one here is seeing the savings claimed it offered.  Unless you go to 2X8 walls one said.  Our architect on our house had a long litany on not doing it.   

[MountainDon]

It may be easier and simpler to build a conventional 2x4 stud wall and apply polyisocyanurate foam sheets on the exterior, vertical furring strips for nailing the siding to.

A builder here uses 2x8 walls filled with blown cellulose which = R31. He says with that the stud loss becomes almost inconsequential. Coupled with R60 ceiling it's hard to beat that.

[Dave Sparks]

It may be easier and simpler to build a conventional 2x4 stud wall and apply polyisocyanurate foam sheets on the exterior, vertical furring strips for nailing the siding to.

A builder here uses 2x8 walls filled with blown cellulose which = R31. He says with that the stud loss becomes almost inconsequential. Coupled with R60 ceiling it's hard to beat that.

Good advice on the sheet foam over strips!  Window placement, window construction, and interior window heat shades are as important as everything else.  Synergy!

[MountainDon]

Have you looked at REScheck? It is software that computes energy efficiencies for different types of wall, floor, ceiling construction. It does not have the ability to compute an offset double stud wall like that but it does have the ability to compute walls with just infill, just continuous (like foam sheet) and both together. Windows, etc are factored in as well.  Many jurisdictions require its use in determining a pass/fail before permits are issued.

[rick91351]

It may be easier and simpler to build a conventional 2x4 stud wall and apply polyisocyanurate foam sheets on the exterior, vertical furring strips for nailing the siding to.

A builder here uses 2x8 walls filled with blown cellulose which = R31. He says with that the stud loss becomes almost inconsequential. Coupled with R60 ceiling it's hard to beat that.

Our neighbor when we lived in the valley was a engineer and their first house they built here was designed around 2 X 8 walls for that reason.  Lived a few years in it and was transferred.  They sold it and have nothing but great thing to say about it.  It was easy on heating and cooling and very quiet.  Almost soundproof to the outside world.  He said it was way over built.  I think they would buy it back in a heart beat.  Soon as they retired they moved back here.  Both were born and raised back near the Great Lakes so this area is almost like snow birding to them.     He seemed to be very good at cost analysis.  Added materials and is it worth it?  Fact he was sort of like living next door to Mountain Don.    

Have you looked at REScheck? It is software that computes energy efficiencies for different types of wall, floor, ceiling construction. It does not have the ability to compute an offset double stud wall like that but it does have the ability to compute walls with just infill, just continuous (like foam sheet) and both together. Windows, etc are factored in as well.  Many jurisdictions require its use in determining a pass/fail before permits are issued.

We are now under RECcheck.....  While I hate controls I think it is a good idea.  It did tack more than a few bucks into the planning costs I think it was well spent.       

[MountainDon]

It allows one to play with more here, less there and come up with a happy average, rather than go by a strict prescription.

[flyingvan]

I haven't looked at a bridged wall yet.  If I were in the insulation business, though, I'd invest in a good Bullard thermal imaging camera and canvass neighborhoods.  You can spot the houses with no/poor attic insulation a long way off.  Metal framed windows stand out.  'A' frames are pretty interesting---cold at the bottom where the people are and hot up in the peak. 

[busted knuckles]

Thank you for all the replies. It does not seem to be worth it. I dont want to go to an 8 inch thick wall. The outer foam board seems like a better idea.

[bayview]

http://countryplans.com/smf/index.php?topic=13443.msg175513#msg175513



/.

[flyingvan]

If you go with the outer foam board, just make sure you account for 'breathability'.  I don't think that stuff is very permeable.  I'll take a little heat loss if it means not trapping moisture anywhere

[upa]

The way we approached thermal bridging was to apply polyisocyanurate foam sheets with a reflective surface on top of the exterior sheathing/2x6 framing fiberglass bat insulation. The foam board only offers a r-4 resistance rating but it effectively eliminated any inner wall condensation/ freezing. The only rub is that is impermeable and acts like a very effective vapor barrier so we elected to eliminate an additional interior vapor barrier that would in effect cause a vapor trap within the  fiberglass batted walls.  On our north wall we used a siding material made of closed cell foam that is claimed to be r7(if I recall correctly). So north wall has R32 rating, remaining walla are r25, ceiling r46(11 inches of fiberglass under an inch of blown closed cell foam), floors have R21 fiberglass with poly vapor barrier on outside. Main heat loss is now minor infiltration at doors, vent openings and through double pane vinyl windows that roughly represent 10% of the wall space. They gave a R rating around 2.4 for the windows. I consider the 1100sq/ft cabin fairly tight and well insulated. I am not sure if there would have been a huge savings to going with double framed exterior walls.

I redid some recent heat loss experiments/ calculation recently. I was able to monitor temperature drop over several hours and note the energy required to recover said loss. I find that 30 degree indoor/outdoor differential equals to approximately 5000 BTU loss per hour, while 45 degree differential requires approximately 9000 BTU to be replaced hourly. I converted this to BTU content of dry white oak and poplar as these are the woods we predominantly heat. The math tells me I should be going through 2.8 cords of poplar in a full 6 month heating season or approximately 1.7 cords of oak. We have only been at the cabin part time but this consistent with actual observed use. Don't you love it when the math is real life reproducible.

[flyingvan]

   What an awesome exercise.  I'm going to copy it, but not for our main residence because I just don't want to know.  I think you are now in a 'law of diminishing returns' point----you'd have to spend a lot more to appreciate any more real gain.
    Even at the big house, the largest source of energy loss is out the front door.  My wife seems to like standing there with it open, chatting with someone she doesn't want to invite in but doesn't want to let go quite yet, furnace/wood stove going the whole time.  Letting it pass is cheaper than a divorce--but not by much

[JRR]

An "alcove" front entrance might make you both happy.

[firefox]

With airlock door locking protocol

[UK4X4]

Airlock door protocol.......

I thinks thats as easy as herding cats....weather here is dropping and being an older house has its issues, we have an internal porch type thing and at the rear an unheated lean too.

My wifes from venezuela, where all doors are open all the time.....so you get natural wind through the house
and getting her to understand that the heat disappears when she leaves doors open is seemingly impossible.

I just seem to be going arround behind her closing doors like a lunatic......

meanwhile the attic has zero insulation......so not sure who's worse her or me in wasting the heat !

[flyingvan]

Looks like option #3 just opened up.  We could move to Venezuela.

[firefox]

I know you were kidding about option #3, but the situation down there makes the
other two options look like a gift from paradise. Enough said.