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7 Answers

Bentonite on basement walls

I recently bought a house in Marine 4C climate zone that has an east facing daylight basement. The previous owner installed an interior french drain that drains into a sump pump. The drainlines for the downspouts were rerouted from the front(west, which slopes slightly into the house) to the north and south sides. The problems they were trying to resolve have apparently been fixed because the interior concrete walls of the basement are not damp and the sump basin is bone dry after above normal fall and winter rains.

In Energy efficiency and durability | Asked By Jeffrey Stark | Jan 10 17
3 Answers

Best air sealing and insulation for knee walls in tray ceiling


I have a single family home in climate zone 5B.The attic is ventilated. I had the attic air sealed and insulated to R50 with blown in cellulose 1 year ago. It looks like they neglected to do the knee walls properly on the great room which has a tray ceiling which is 3 feet high (see photo). They just wrapped the knee walls with batt insulation and otherwise didn't do anything else.

1. What would be the best options to air seal and insulate the knee walls?
2. Is this difficult to do since the attic now looks like a winter wonderland?

Thank you

In Energy efficiency and durability | Asked By Stan Weinstein | Jan 11 17
8 Answers

Mixed roof insulation methods


We are building a home near Ann Arbor, MI and would like some advice on how to approach a specific portion of our building section.

The majority of the home will have R60 blown in cellulose (blue areas) with Intello Plus underneath. The vaulted (red) area will be R60 closed cell foam. The walls will be EIFS, 2x6 R20 Roxul with 4" EPS exterior foam.

Our concern is the clerestory wall (green and purple).
We will continue the EIFS on the exterior portion of the wall (green), but are a little unsure what to do on the vented ceiling/interior wall (purple) section.

In Plans Review | Asked By Eric Burhop | Jan 11 17
4 Answers

Keep or remove whole house fan?

Our house in SE Michigan has both AC and a whole house fan that I know is resulting in a huge loss of heat during the winter (and likely similar loss of conditioned air in the summer).

Currently we just have a sheet of R5 rigid foam screwed to the ceiling to block off the hole (ugly, but it works for now).

Currently debating between two options:
1. Remove the fan, drywall over the hole, & cover with insulation (less time & money, better insulation, less flexibility for cooling)

In General questions | Asked By Timothy Tucker | Jan 10 17
3 Answers

How to get rid of that creep in the wall?

My design challenge has been to apply the concept of “outsulation” , 2.5” exterior XPS rigid board, to a wood structure that will ultimately have 3 coat stucco and real stone veneer as final exterior. The project is in Zone 5, new construction, 2x6” wall, stick framing. Have gotten some good insight from Martin, who has directed to me some valuable resources, as well as fellow GBA readers. Ultimately ran it past a local engineer, between his input and the cumulative experience gained by reading, eventually abandoned the idea. Too risky, too much weight, not a proven assembly, don’t do it.

In Energy efficiency and durability | Asked By Sal Lombardo | Jan 10 17
14 Answers

What do you think of this wall makeup?

I've spent countless hours researching (new to energy efficiency,) and I've finally decided on a wall design for a new construction house I'm building. Curious as to what you think.

Location: CT (Zone 5)

1/2" Gypsum Board/Latex Paint
2x2 horizontal strapping with Roxul ComfortBoard 80 (1.5", R6)
2x6 wood studs 24"oc with Roxul R23
7/16" ZipSystem, taped appropriately
(2) layers 1.5" foil faced Polyiso, outside layer taped
1x3 strapping
Hardie Board siding

Effective R-value of both Roxul products: r23.42
Putting an R value of r5/in on the Polyiso: r15

In Energy efficiency and durability | Asked By Adam Nickerson | Jan 9 17
1 Answer

Fan efficacy and ERVs

what classification does a erv/hrv have if it doesn't have a ECM motor
it is not exempt from the efficacy requirement. so, does it a bathroom utility roon fan efficacy

Panasonic whisper comfort erv uses an ac motor .\
its fan efficacy is 40 cfm@ 0.1 esp/ 23 watts = 1.75 ?

In Building Code Questions | Asked By Kevin Mick | Jan 11 17
1 Answer

3 ach50

Is there a way to know what the infiltration will be in a house after it passes the test?

If an exhaust ventilation system is used for ASHRAE 62.2 requirements, how do you know that sufficient makeup air will come in through cracks to compensate for what is exhausted?

In Mechanicals | Asked By Kevin Mick | Jan 11 17
2 Answers

Vented and unvented ceiling, Zip System, metal roofing, underlayment question

I am seeking some advice, and have been researching for quite a long time, but can't really seem to find the best answer for our situation.

Currently building New Construction in Climate Zone 5. Using ZIP System for the walls and roof.

In the center of the home, we have Unvented Cathedral Ceiling. We decided to use Unvented design, and insulate with Closed Cell Spray Foam.

On the two sides of the home, we have Vented Ceiling, with unconditioned attic space, insulating with fiberglass batts.

We plan on installing a metal roof.

In Energy efficiency and durability | Asked By Bridget Lamberson | Jan 10 17
4 Answers

Rigid foam, vapor barriers, and moisture issue avoidance

I am in process of picking 3" of EPS product for under my slab, around my stem wall and exterior wall CI. I have read through posts on GBA and articles on the Building Science website such as here that state the following is something to avoid, especially when using exterior rigid foam in your wall assembly:

In Green building techniques | Asked By Joshua Greisen | Jan 10 17
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