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0 Answers

Passive solar design and HVAC sizing

I just used software (free to use online) to do a Manual J. analysis of my heating and cooling needs, since I just found out that I may need to replace my 13 year old HVAC system. One of my 2 heat pumps has a leak and needs to be recharged, and I am considering my options, so I wanted to get an accurate estimate of my heating and cooling needs. I found that the Manual J. heat loss calculations do not take into account the heat gain from the passive solar design, (except for cooling loads).

Asked By Ron Nachman | May 22 17
9 Answers

Insulating polyiso with EPS in a roof stack

Has anyone tried protecting the R-value of Polyiso by putting it inward of EPS?
We are contemplating insulating a roof deck with an over-deck foam stack.
We are in Zone 5A (Lake Effect, N.E. Ohio) and the idea is to maximize R-value by using "some" Polyiso. In an attempt to maximize the R-value with a 6" foam stack here's what we have come up with. From inward to outward:
1) Rafters
2) Zip System OSB Decking
3) 2" Polyiso (R-6.7)
4) 2" EPS II (R-4.2) - Staggered
5) 2" EPS II (R-4.2) - Staggered
6) Roofing Membrane
7) Furring and metal roofing
Total R-value of 30.

Asked By Dave-OH | May 19 17
12 Answers

Sealing PT sill plate to concrete slab ?

I am a homeowner in the midst of a 2000 sq ft addition. Houston TX, foundation is a concrete slab. Walls (from inside out) are drywall, stick 2*4 framing with open cell foam, OSB, tyvek, air gap, brick veneer.

The builder used pressure treated 2*4s for the sill plate but there is no (capillary) barrier between the concrete and the sill plate. 3.5" of open cell spray foam is going in the exterior walls today.

Asked By Mark McFarlane | May 20 17
5 Answers

How to deal with duct-work that installed in unconditioned attic and a powered attic ventilator?

I am a homeowner of a brick ranch built in 60s in climate zone 7 and it is about 1,800 sqft.

The previous owner had the furnace and ductwork were installed in the attic and a powered attic ventilator (PAV) too in 2013. The attic floor does have some fiberglass as insulation material and it is about 8 inches. The ductwork is insulated flexible duct (supply duct is black from the outside and the return duct is silver from the outside).

Asked By TedLiu | May 22 17
3 Answers

How to insulate kneewalls or interior gables?

I have a room with a vaulted ceiling. The interior gable wall obviously extends to the ridge. On the opposite side of the gable wall is a vented attic space with insulation on the attic floor. I would like to insulate this gable wall against the attic.

Asked By Bob Brown | May 21 17
5 Answers

Ice & Water Shield and closed-cell foam for an unvented roof?

I'm looking to add exterior insulation to a low-slope wood decking (2x6 T&G) roof.

I have come across details that use rigid foam, but the builder would like to use a purlin system to create a cavity for closed cell spray. My question is, if we go that route, would I still want a peel & stick air-barrier applied to exterior of decking and interior of the purlin/spray foam layer if the closed cell will act like an air barrier.

Bonus question, should the eaves be insulated to reduce ice-damming?

Thank in advance.

Asked By B B | May 20 17
1 Answer

Heating a "near passive" house?

Hi everyone, I am currently mid way through the design of the home we will soon build. Coming from a traditional carpentry background and this will be our first 'superinsulated' build. We are not going for passive cert. but building with passive methods and ideas.

House is 2 levels, Walkout basement with lots of south facing windows. 2800 sq ft total.

We are in zone 6B in BC Canada, and aiming for wall R40 roof R60, using the dual stud wall method with cellulose insulation.

Planning to heat the house with a wood fired boiler, and having electric as backup for when we are not home.

Asked By user-6850466 | May 20 17
10 Answers

Adding rigid foam above rafters but below ventilated roof deck

Hi all, wondering if this plan will work:

Climate Zone 6,Nova Scotia Canada
Simple geometry of roof.
Trying to create a ventilated roof system.

Rip off rotten roof sheathing.
Lay 3inch EPS rigid foam over top of rafters that are every 24 inches. R11-12
Planning on screwing on 2 by 4s on the flat from eave to ridge right above the rafter, effectively sandwiching the EPS foam between the rafter and the 2 by 4s.
Screwing on 5/8 plywood as roof deck onto the 2 by 4s, creating a ventilation gap between eps and roof deck.
Adding Nova seal as Ice and water shield.

Asked By user-6848033 | May 20 17
6 Answers

Eliminating musty odor under a low-sloped (flat) roof

Hi Folks,
I have read all the info that I can find about low slope flat roofs, insulation and the possibility of venting.
But I am still unsure of how to proceed with my house problem.

Asked By Steverts | May 17 17
4 Answers

Is there an advantage to having radiant barrier sheathing on the roof of a house which is rather cold in cool weather?

we have an old shake roof on a house that was built in 1947 in the mild climate of san jose, california. the house is generally cold and damp in cold to cool weather.

we are now replacing the roof with a shingle roof. we were told that the new roof may help with the chill as there will not be gaps between the 'rafters."

we are trying to decide whether to buy radiant barrier sheathing for the warm to hot days, which have been hotter and more numerous in the last few years. however, we do not want to make the house even colder outside of the times of heat.

Asked By ms49 | May 18 17
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