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9 Answers

Indoor Humidity - dew point & monitoring condensation

I live in Colorado, Zone 5, where our winters frequently drop down to 0-20F and outdoor humidity levels might be in the teens.

I recently figured out my chronic congestion gets about a hundred times better at 45% humidity. Despite all the sealing & insulating we've done, the plants and three dogs, our house drops down into the twenties in winter, sometimes even the teens. Because this is a retrofit, I probably can't hit 0.6ACH. I'm around 1.5ACH right now, and the next sealing & insulating step will require ripping off the roof, so that's on the back burner.

Asked By pshyvers | Dec 11 17
5 Answers

Help selecting a heat pump

Hi Guys,

I'm going to be meeting with my builder this week, and he wants to show off the furnace of his choice, which is a Dettson Chinook. It's a small modulating natural gas unit, that can be paired with their Alize heat pump.

It's a pretty neat unit, designed to allow for very long cycle times, often measured in hours. The problem I have is that the heat pump portion kind of sucks in cold weather, it uses proprietary small high velocity ductwork, and a proprietary thermostat to control it all. It also has a short~ish warranty.

Asked By Stephen G | Dec 11 17
9 Answers

1952 Cape Cod


First-time poster. In the past 2 months, I’ve read a hundred or so GBA articles and comment threads; I’ve been amazed by the expertise and generosity of the community. I’ve also read extensively at buildingscience and finehomebuilding -- I’m new to but very interested in building science. Here’s why:


Asked By Emerson W | Dec 11 17
10 Answers

Repair or replace sheathing behind brick veneer

I wanted to get some advice on what to do with existing sheathing material that is currently installed behind brick veneer in a 1980's home I'm currently renovating. It's located in Houston, is 2x4 wood frame construction on concrete slab foundation, and the other parts of the house have T1-11 and vinyl siding (which will all be eventually replaced), but my questions concern what to do behind the brick for now. Much of the interior has been gutted down to the studs due to issues with mold and pests.

Asked By sdcnyhou | Dec 8 17
8 Answers

Drain Water Heat Recovery

I plan to install a drain water heat recovery unit in my new home. Does anyone know of any guidelines on sizing? For example,there will normally be 2 people in the house, but on occasion that could easily double or more as we have extended stay guests (a week or even more). And we will have a 65 gallon heat pump water heater.

As the DWHR units tend to get pricey due to the copper involved, I want to make sure I get the most bang for the buck.

Asked By Norman Bunn | Dec 11 17
6 Answers

Insulate "crawlspace"

I put crawlspace in quotes because this is more of an unfinished basement with dirt floor. The joists above range from 7-10' above grade. The floor slopes 5' in the middle. I currently have no plans to finish the basement.

The house is in Zone 6. I want to make it more cost effective for heating and keep the moisture controlled.

My plan is as follows:
1. put 15-20 mil plastic over the current plastic sheets which has been walked on and is now covered in holes. Re-attach to foundation and seal using tape.

Asked By James Bodell | Dec 11 17
6 Answers

Exterior foam with stone and 10 mm rainscreen

I am planning to build a new house and I have a couple of questions.

The house will be in climate zone 2 - hot-humid (near Houston, TX). The walls will be 2x6 with 3.5" of open cell spray foam. The walls will be sheathed with OSB and we are planning to add 0.75" of foam board (R4) on the exterior and use Tyvek drainwrap and a 10 mm rainscreen (i.e. MTI Surecavity).

Some of the walls will have a full stone veneer (3"-5" bed). Some will be half stone and half Hardie and some will be all Hardie. My questions are:

Asked By E247 | Dec 5 17
1 Answer

Exterior Mineral Wool Insulation: Batts vs denser boards

I am planning to add exterior mineral wool insulation over the exterior of my double wythe brick walls. The typical choice is high density boards such Roxul comfortbatt 80. They are substantially more expensive than the medium density mineral wool batts that typically go into stud bays on the interior such as Roxul Comfortbatt. I think the price difference is factor 3 at least on a $ per R per sqf basis. Hence my idea: Attach a 2 by 4 on the flat with Tapcons to the brick.

Asked By matthias paustian | Dec 12 17
7 Answers

Insulate a cathedral ceiling efficiently

I just bought a house in Northern NH, zone 6 that was built in 1987. The house is about 3300sq-ft on 2 floors, so about 1600 sq-ft foot-print. The main living/top floor is entirely cathedral ceiling.

Asked By James Bodell | Dec 11 17
15 Answers

How to tell if I need a HRV?

So at the conclusion of my home energy audit, it was recommended that a heat recovery ventilator be installed because my house (built in 2002) is already too tight.

I always though excessive wintertime moisture was a good indication that a HRV was needed. However, the humidity level in my home drops to about 17% in the dead of winter. Isn't this an indication that I already have a ton of air infiltration?

I'm very confused and wonder if the auditor performed the blower door test incorrectly. Could the forced air system be the culprit for the dry air?

Thanks in advance!

Asked By BuildingNewb | Dec 10 17
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