How your house is losing heat: thermal bridging explained

In this video we talk about one major form of heat loss in most homes, thermal bridging. We go over what it is, how to tell if you have it and how to prevent it while building.

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[olsenswe]

I find it facinating that a 7, 5 inch thick wall vould be considered a problem?

Here in Sweden, in order to meet code you usually have to build a 12" thick wall and have 20-25" of insulation in the roof. A vapor-barrier is placed on the warm side of the structure in order to prevent moisture to diffuse in to the wall. On the inside of the vapor-barrier, a 2-3inch "service cavity" is build so water- and electrical installations can be made without compromising the vapor-barrier.

[maxnewby]

Thanks for a very clear explanation of the problem with thermal bridging, in Canada a lot of emphasis has been placed on the need for continuous tight vapour barriers on the inside of exterior walls and ceilings and the use of vapour barrier coatings e.g. alkyd or oil based paint, especially in retrofit situations.

[AndyFromm]

My house was built in the mid 80's by high school students. It has exterior walls 12" thick, staggered 2x6 walls to reduce thermal bridging. I built the same house in that class in the late 90's.

[rogerbettencourt]

Wow! Always enjoy your factual approach without the need of any “reality” show appeal. Thank you guys so much.

[jefflabrozzi]

Nice explanation it is very complicated to get this correct especially when considering window and door trim work. If not done correctly you can create a lot of extra work. Much appreciated .

[mikewatson]

Very good explanation of the problem and various solutions. Thank you. Keep warm

[bobbray]

My approach in zone 6a was Zip-R12 sheathing and closed cell spray foam between my 2x4 studs. This creates R-30 walls which are the same thickness as 2x6 studs and accommodates most windows without custom window/door extensions needed for thicker walls. My wall studs are R-15 instead of R-5, if building with 2x6 studs and no exterior insulation and 5" of sf. For my home, about 925 sq.ft. are wall studs and headers, so insulating with exterior insulation makes a big difference overall for energy consumption.

By using Zip-R12 sheathing (2-1/2" thick), we didn't need window bucks. We used 4" exterior structural screws on the window flanges though the Zip sheathing and into the window framing. Overall our labor cost was much less than installing regular sheathing, window bucks, exterior insulation, a WRB, and furring strips for siding installation. Also made it much easier to make sure everything was installed correctly, since using ZIP-R was pretty much like installing wood sheathing. Just needed to tape the seams and window openings with ZIP tape to make the assembly air and water tight.

[kindredcouches]

Took a walk today after watching this video to scope out the neighborhood roofs and see who's the most insulated.

[siriosstar]

When mass timber is used ( CLT or logs) instead of sticks/studs and insulation is applied to the outside, the wall then becomes a storage medium for heat as well as a humidity controller due to the hygroscopic effect of wood . The entire assembly is vapor permeable .
For example my house is made of 14 cm thick laminated beams/logs with continuous wood fiber insulation panels on the outside, also 14 cm thick . then vertical furring strips are installed to secure the insulation and to accept the desired siding . the space between the furring strips acts as a vent to remove moisture build up . the channels are open at the bottom and top to create air flow .

[christophermeixell]

Heat exchange takes all paths - not just the path of least resistance. Some heat goes through even the most insulated part of the house. It's like water in a burlap bag - it weeps from everywhere, but if there are holes in the bag, it flows faster there.

[andreabeydler]

The best explanation i have heard on this subject. Would something like havelock wool help?

[bastiat]

You could also talk about double stud walls where there is a space between the interior and exterior wall, and where you stagger the studs so that the interior and exterior studs aren't on center of each other but staggered to increase the cavity size between studs and the other side.

[brianprince]

If you have an attic and the insulation is on the ceiling (so not on the underside of the roof), and are seeing exterior roof stripes, wouldn’t the roof probably be getting warm in between the studs/trusses in this case?

[hectormarcayda]

Sir. Building a custom home in Northeastern WY. Your information is of great value. A point of clarification on your continuous insulation concept. Am I correct in assuming that insulation should either be on the outside of cavity insulation or the inside, but not both to prevent condensation and moisture from being trapped (and thus leading to mold, etc., etc.). I was under the belief that you should have insulation on the inside and outside of the cavity. I hope I correctly articulated my questions. Thank you.

[johnritchie]

Very helpful explanation. Can I ask how a Zip R panel works then? If the foam is on the interior side of the sheathing is that accomplishing the goal of keeping the dew point of the sheathing at an acceptable level?

[guytech]

Don't go with SIP walls as it very difficult to route utilities (electrical, plumbing, low voltage wiring). SIP is OK for roofing, but a real pain to work with for walls.

[guytech]

Nah, best option is continuous exterior foam panel insulation and 24 OC 2x6 exterior wall construction. That will provide the most bang for the buck. Once you get into double studded walls the complexity & cost goes up for diminished returns of reducing heat loss.

The most heat losses in a well insulated home are not from the walls, but from windows, doors & vents. Door heat losses can be reduced, by using fiberglass exterior doors with multi-point locks for a tighter seal. For vents (dryer, bathroom, stove, etc) install a vent backdraft damper on the exterior side of the vent pipe. Insulate the vent pipes. For windows, installing fewer & smaller windows helps.

[ajhearn]

If you go with sips and timber frame do you still require a vapour barrier on the inside wall? Same question for the zip r system

[PeterLee-znjl]

Thermal paths are IMPORTANT
DEW POINT IS LIKEWISE..
VAPOR PRESSURE IS THE REAL TRANSPORT OF TEMPERSTURE...
REGULATING VAPOR IS THE ISSUE..
HMMM

[alexv]

Unfortunately, this video fails to show the “REAL MEAT”—the ACTUAL, PHYSICAL EXAMPLES of materials—that solve such heat losses. I felt it was created more as a teaser to bring people in.