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2 Answers

CMU walls and rigid foam

Retrofit concrete block walls painted inside and out. Exterior foam then rainscreen then siding. Keeping painted block as interior walls.
Do I have to be concerned with the vapor permanence of the foam?
Also, would there be any benefit in using foil faced...other than R-value?
Southern Georgia coast.

Asked By Robert Brown | Aug 29 15
4 Answers

Unvented Roof, 3B, Foam-Free

Hi Martin,

First off, I have read a wealth of articles on the subject of unvented roofs, by yourself and Joseph Lstiburek. I started with your “How to Build A Cathedral Ceiling” article and read pretty much everything related to this from you and Lstiburek. The conclusion being that for an unvented roof you either install closed-cell spray foam between the rafters, or rigid foam above the sheathing at a thickness dictated by your climate zone to keep the sheathing warm enough.

Asked By Joe G | Aug 26 15
15 Answers

Humidity control

I operate a facility where humidity control is very hard. The building is 6 yrs old, built well, but cant control the humidity. We have resealed return duct, replaced tstats, added attic exhaust fans, etc. But still the building humidity matches the outdoors as fast as it changes. We try to keep the building 72f and it feels like you can't breath and hot. Mildew forms. We keep the building 68f you can breath, but freeze and smells like a basement, and mildew forms. All exhaust fans are working, and ceiling fans are on.

Asked By clark jones | Aug 24 15
1 Answer

Furring strips or another layer of sheathing over foam?

I am in the process of framing a house 2x6, 24”oc. The house will be sheathed and taped with the Zip system and 2-1” layers of rigid foam (staggered seams and taped). Over top of the foam, I planned on using 1x4 or ripping down ¾” ply for furring strips to both hold the foam and attach the vinyl siding too.

Asked By Brian McDonald | Aug 27 15
2 Answers

What is your opinion of the CERV HRV system?

Looking to add an HRV to a new home plan, 2500 sq.ft.

Concerned with humidity levels in Massachusetts. Very humid summer. Dryer winter. House will be close to net zero.

Asked By Joseph Isherwood | Aug 26 15
2 Answers

What can I do to address a condensation and mildew issue on a cathedral ceiling?

Our house is 35 years old and has a cathedral ceiling in the living area located in the center of the house. We have never had an issue with the ceiling until about 5 years ago. Condensation develops during the summer months on the ceiling and ultimately results in mildew that spreads across the entire ceiling. We live in LA and the heat in the summer is in the 90s during those months. Approximately 8 years ago we replaced the roof on the house, using the architectural shingles and removing the power vents and replacing them with a ridge vent system.

Asked By Susan Cochran | Aug 24 15
3 Answers

Rain screen at soffit detail

CMU house in zone 2.. Hot/humid. Unvented conditioned attic, Rigid foam around rafter tails to underside of roof decking. Cedar shingle sidewall. Verticle and horizontal furring for rainscreen.
Here's the question: There is a plate at top of the wall but due to the slope of the roof the horizontal soffit line falls below the plate line. For added support I would like to run the verticle furring up to and attach to the top wall plate. This means the top of the rain screen will terminate in the unvented soffit.
Do I need...and how do I accomplish ....the top rainscreen vent. Thanks

Asked By Robert Brown | Aug 24 15
7 Answers

What ceiling insulation to protect against ice dams in winter time?

I have very low ceiling less than 8 ft.
I don't want to lower the ceiling. But there are not enough space for insulation.
I wan to use Hard foam to insulate the ceiling having 4 by b joist.
There are two options.
1. Using 2 inch hard Foam(r-13 ) with radiant barrier. (Therefore, there are 1.5inch airspace above the radiant barrier )
I want to install the barrier to reflect inside heat to the room so that I want to make the ceiling being cold.
2. Uisng 2inch hard foam (r-13 )and 1.5inch hardfoam(r-9) together without the radiant barrier. No air space.

Asked By Mansig Yoon | Aug 22 15
1 Answer

Rigid foam and rafter tails

The attic is conditioned space due to foam spray on the underside of the roof deck. Foam also fills the void between top of wall and roof deck. So, when I install my exterior rigid foam should I stop at the top of the wall or cut out for rafter tails and continue the foam to the bottom of the roof deck.

Asked By Robert Brown | Aug 12 15
3 Answers

Mitsubishi mini split questions

I am replacing an old heat pump in my Boston area condo unit (middle floor and attached units on each side). I wanted a hyper heat ductless mini split (Mitsubishi FE series) but it only goes to 18k btu. Would I be better off with this or with the GE series which is sized correctly (24k btu)???
The contractor wants to leave in the old (1985) heat pump as a back up. Does this make sense?

Asked By Ann Shef | Aug 11 15
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