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4 Answers

How do I thicken slab with 2" of foam underneath?

I am building a house on a slab (with in-floor heat). There will be 2" of blueboard underneath the entire slab. I need to thicken the concrete slab16"x8"x10 feet in the center. How do I do this and maintain the continuity of the insulation? Pour the pads first? Cut holes in the blueboard? Help, I start next week!

In Green building techniques | Asked By Charles Eichenlaub | May 22 12
2 Answers

Sill/band-joist: open or closed cell?

I'm planning a DER that includes external polyiso installed down to
the foundation wall, thus covering the sill and band-joist. The
contractor has specified closed-cell sprayfoam on the *inside*
of the sill and joist area to help air-seal and further insulate
that area. The sill is directly on top of the cinderblock wall
without any capillary break that I can discern; it's sufficiently
above grade that most moisture problems that might create
don't seem to be an issue. However, I'm concerned that since
there is invariably a little bit of moisture drive upward from

In Green building techniques | Asked By Hobbit _ | May 21 12
5 Answers

HRV preheating with hydronic coil.

I am a Building inspector in Yellowknife NWT - -52 celcius design temp. I recently had an email discussion with a mechanical contractor who puts heating coils on the cold air inlet of the HRVS he installs, mostly venmar constructo's. it went something like this.

ME. Heating coils on the outside air intake to the HRV. This destroys the efficiency of the HRV, as the temperature differential of the intake and outlet air is very close, so there is less potential to remove heat from the outlet air.
If customers want to temper the air coming out of the supply, this can be done after the HRV.

In Mechanicals | Asked By luke forssell | May 15 12
1 Answer

Could old wood make us sick?

We are redoing bathroom in a house that is around 120 years old.The bathroom was an add on 60 or so years ago, they left the old boards from outside of the house on as part of the walls.

We have been ill since we started this project. Every time we cut wood or sand it we have upset stomach,dihreha, headaches. It only happens to the ones working in this room!

Could there be something in the wood itself from when it was put on the house? There is no mold at all, smells of old wood. When we use the respirator mask we are fine.

In General questions | Asked By penny zoellner | May 23 12
5 Answers

Which is a better system: a regular fan coil or high velocity fan coil?

Hi,
I am building a custom house for a customer. He will have in slab heating throughout the house, and I have suggested to my mechanical contractor to include the hi velocity fan coil. He says that the regular fan coil is better. Any advice would be greatly be appreciated.Thanks

In Mechanicals | Asked By Elio Gabucci | May 16 12
4 Answers

Will furring strips be needed over sheathing if using steel roofing?

I'm Zone 5 - upstate NY, planning to build 1050 s.f. ranch home, using r-20 superior wall basement, r-33 double wall cellulose.
If i build roof using 2x10, and gusset 2x4 underneath, filling with cellulose, and if i use 1" foam board to baffle/vent roof 1-1/2" beneath sheathing, i could obtain over r-43. here are my thoughts/questions

In Green building techniques | Asked By steven bumpus | May 21 12
2 Answers

Help deciding which Mini-Split HVAC to buy

I'm following advice from a previous question I posted here and planning to install a mini-split in my garage apartment. Various sources and calculations indicate an 18,000btu unit is optimal. I'm thinking of purchasing one online, doing some of the less technical work, and having my AC technician do the final hook ups, etc. I have a few questions inhibiting progress.

In GBA Pro help | Asked By Dorothy Prowell | May 20 12
2 Answers

An article on Chris Corson's Passivhaus in Maine

Here's a link to the new JLC article on Chris Corson's Passivhaus project in Maine:
An Affordable Passive House.

Nice work, Chris.

If you are interested in more information on Chris's project, you might want to read the GBA story about his house: Striving for Passivhaus Affordability.

In PassivHaus | Asked By Martin Holladay | May 17 12
2 Answers

Retrofit Vapor Retarder/Barrier in Ceiling Plane

I finally crawled up into my attic of the house I purchased four months ago. I knew that I needed to add significant insulation (currently has about 6"-8” of loose cellulose) as I want to get to R60. In advance of adding the additional insulation I am air sealing the attic. I was digging around in the insulation to find the various wiring penetrations, to foam them closed, and I was immediately struck that I didn’t find poly (or any other vapor inhibitor) on top of the ceiling drywall, as is the typical scenario in homes in my area.

In General questions | Asked By Pete Marthaler - Zone 7 | May 18 12
9 Answers

Combined HRV and mini-split ?

Are there commercially available units which combine heat-recovery ventilation with an air-to-air heat pump?

I'm imagining something that could transfer heat from the exhaust duct to the supply duct of the HRV as needed during the heating season and vice-versa in the cooling season. Heat transfer within the HRV would be wholly conventional and the additional heating/cooling would be introduced in the duct supplying air from the HRV to the house.

In Mechanicals | Asked By Interested Onlooker | Mar 5 10
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