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3 Answers

Foundation detail...

I've been developing my "poor man's thermomass" for some while and hope to get some feedback on a few points. First of all, after looking at many many many other foundation details with exterior insulation, I'm still not confident that this arrangement of insulation sufficiently creates a thermal break. Missy discussion is about insulated basements but this is slab on grade.

Below 4" slab is 10" recycled glass Poraver beads. This is on top of compacted gravel. At the Endeavor Center, they put 6mil poly below poraver. I'm worried this created a "bathtub" situation.

Asked By Ethan T ; Climate Zone 5A ; ~6000HDD | Jan 21 18
18 Answers

Cycling of heat pump

I have a Fujitsu heat pump with two indoor units each in relatively small rooms. (For good or bad, this decision was made because I was not satisfied if only one room had a unit that sufficient heat could be transmitted to the second room and I wanted each room to have its own thermostat. I recognize that they are larger than I need but I did not see good alternatives) Currently both units are set on "minimum heat" (50 degrees F) because the rooms are not occupied for days at a time.

Asked By David Martin | Jan 14 18
4 Answers

Foundation Uplift

I am planning to build a 2 story standard colonial (28 x 36) in lower Michigan using Sips upper walls and a PWF conditioned crawlspace foundation. I am somewhat puzzled by how uplift is prevented in some of the PWF recommendations I see proposed. I will not be back filling the interior walls so it appears there are 2 options. Pour a 3-1/2" concrete floor( attach to wall via a screed board with embedded fasteners) or build a treated regular joist floor?

Asked By William Oldaker | Jan 21 18
2 Answers

Eave detail

Hello again! For the most part I'm pretty confident in this wall/eave detail, but I'm open to criticism.

My main concern is the long term viability of the "exposed" membrane above the IJoists. I haven't called it out specifically, but I'm assuming it's a fancy vapor item WRB of some kind.

Along the lines of a recent post here regarding longevity... is it foolish to leave the WRB in the open here? The intent is to create a cold roof.

Asked By Ethan T ; Climate Zone 5A ; ~6000HDD | Jan 21 18
4 Answers

New house CZ3, ducted HVAC & air handling design questions

2500sf single story 3 bedroom north bay, California house with conditioned rat slab crawlspace. 3 bathrooms, family rooms with a gas fireplace, "great room" kitchen/DR/LR is 30x42.

Plans call for 2x6 walls with 1" of well sealed foam (exact type still tbd), 500sf of casement windows and french doors with sub-.30 ufactor glazing, unvented 6/12 exterior pitch scissor trusses.

Asked By Rob Hunter | Jan 21 18
0 Answers

How to insulate and finish basement when there are signs of efflorescence?


I am re-finishing/insulating my basement in a 1930 home in Zone 4 (Pacific NW). I am planning to do it as follows from foundation to interior which meets local building code: Basement Concrete Foundation Wall > 1”XPS Rigid Board(Pink Owens Corning) > 2x4 Studs against the XPS > ROXUL insulation in stud cavities > Sealed Poly Vapour Barrier > Drywall.

There is evidence of white efflorescence on the basement walls indicating that there may be or has been in the past moisture seepage. There have been no flooding events. Being a 1930 house, the foundation is not waterproofed.

Asked By J2D2 | Jan 21 18
17 Answers

Thought experiment: 30k cistern as thermal mass in passive home

Hi, we have a mountain lot in Colorado at 7500 ft elevation with lots of south facing solar heat gain, and we're planning on building a passive home. We're required to install a 30k gallon cistern for fire protection. A 30k gallon buried cistern seems to be extremely expensive, while a 30k gallon bladder type cistern is very cheap and could be installed inside the home's envelope in a crawlspace. Assuming the passive home is well balanced for on average for a year, could the huge amount of thermal mass help moderate an even temperate, or would it become a problem?

Asked By Mike AbiEzzi | Jan 9 18
1 Answer

Header Hangers vs. Jack Studs - Thermal Bridging

Advanced framing articles all seem to advise the use of header hangers instead of using jack studs. The idea is, less wood and more insulation in the wall, and better the thermal performance.

Has anyone studies whether the thermal bridge of a jack stud is better or worse than a header hanger? A jack stud is very large by comparison, but a header hanger is a relatively heavy gauge piece of steel that bridges right from sheething to drywall.

Beyond the thermal bridge, could a cold spot behind the drywall cause moisture issues or condensation on the interior surface of the wall?

Asked By Lance Peters | Jan 21 18
0 Answers

Rim Joist External Insulation and Air Barrier - How To?


I plan to recess my rim joist so that 2" EPS can be added as a thermal break. This will be flush with the studs so my sheathing can cover the whole area. Pretty standard.

I want to bring my vapor retarder (Intello or Membrain) out and around the rim joist so it attaches with the vapor retarder on the inside walls. This should result in a seamless air seal from foundation to trusses. Again, pretty standard.

My first question is, does the 2" EPS go on the inside or outside of the vapor retarder and why?

Asked By Lance Peters | Jan 21 18
6 Answers

Insulation with best life expectancy and low embodied energy?

I'm researching insulation options. I want to keep embodied energy down, but also want to have something with a life expectancy of centuries, not decades. Although I've mostly nixed SIPs (PU) because of it's high embodied energy, if it lasts centuries while other insulation materials last decades, then should it be considered? I've also been finding different opinions on the life expectancy of SIPs. Some people say 300 years, others say 50-100.

Asked By Mike AbiEzzi | Jan 19 18
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