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7 Answers

Help me understand static pressure in ducted minisplit systems

Hi all,

Tried to piggyback a comment on this thread (, but I guess the thread is too old and my comment was marked as spam.

I am planning a ducted mini split for the 2nd floor of our home. I have run manual J calculations and find that a Fujitsu 9RLFCD will fit the heat/cool load, assuming I can distribute the BTUs to all the rooms.

Asked By Clay Whitenack | Aug 16 16
51 Answers

Mooney floor

I want to put insulation on top of a concrete floor.
A layer of foam + plywood bolted to the concrete has been suggested. (By Dana I think)
While that looks an good option I've been exploring more low cost options.

What about a Mooney wall, flooring variation.
Thinking about 2x4 + 2x4, filled with blown in cellulose. Likely GreenFiber or InsulMax.

Is that a good alternative?

Asked By Tony Tibbar | Aug 6 16
2 Answers

Spray foam in roof deck — Is lower R-value than minimum code recommendation OK?

I am remodeling a 106-year-old home in Climate Zone 4A where the minimum recommended attic value is R-38. A local spray foam contractor, with a large national company, told me that with spray foam a much lower R-value is OK. He quoted the job at R-20 for the roof deck. I know that air sealing is of paramount importance but it seems R-value also is important.

Is R-20 really enough?

Asked By Ross Williams | Aug 21 16
19 Answers

How should I address the lack of plywood boxes for my double stud wall rough openings?

Blame it on lack of clarity on my part, but when my framer built my double stud walls he didn't oversize the window rough openings to account for 1/2" plywood sheathing connecting the inner to the outer walls. He figured that this gap could be covered solely with drywall.

What is the disadvantage of not having plywood in this location?

Asked By Adam Peterson | Aug 12 16
10 Answers

Fiber-faced rigid foam as basement insulation?

I have some extra fiber faced rigid foam sheets that I have left over from our build. Would this be OK to use as wall/floor insulation for a small crawlspace? The fiberglass facing has me wondering if it will be a problem.

Asked By Clay Whitenack | Aug 11 16
1 Answer

Should I use this foam?

I recently got a bunch of polyiso foam pieces that I want to use on the outside of my house. The outside of the house has 4" of foil faced polyiso, but I have many attached porch roofs that have nothing between the rafters where they attach to the house. I was going to cut and cobble pieces in these spaces and can foam the edges. Here lies the issue, the foam I just got is 3" thick so I was going to double them up but I'm not sure about the facing. One side is a layer that looks like tarpaper and the other side looks like 1/2" of sound board, seems similar to suspended ceiling tile material.

Asked By darren williams | Aug 13 16
8 Answers

Is it better to combine an ERV with an air handler or ductless mini-splits?

We’re building a tight house (the Passive House metric of .6 ACH is the goal) with a significant amount of insulation (slab to attic R-values: 16-20-38-65) in the Chicago suburbs. Our house will be about 1,550 sq. ft. of finished space, single story, 2-BR, 2 bath, with a full basement.

I always assumed the HVAC system would be a basic combination of ERV and ductless mini-splits (for heat and AC), but our HVAC contractor is suggesting the following set-up:

Goodman air handler with 15K.W. Heat strips, for supplemental demand
Goodman 2 ½ ton Heat Pump 14.0 seer

Asked By Eric Whetzel | Aug 12 16
4 Answers

How to install fiber-cement siding over mineral wool?

I am planning to install 2" thick Rockboard 80 over Zip Sheathing using vertical furring strips screwed to the 24" OC studs. I am planning to install fiber cement siding on the outside of this assembly. I have two questions:

Are 1x4 furring strips thick enough to provide adequate material for the fiber cement fasteners to attach to?

Asked By Timothy Godshall | Aug 12 16
5 Answers

Flashing a shed dormer with mineral wool exterior insulation

We are using exterior mineral wool insulation, but can't find a detail for where the side wall of a shed dormer meets the roof.

1. Where does the step flashing go - taped to the Zip sheathing or outside and under the mineral wool?

2. If the flashing goes on the Zip sheathing, should the bottom of the mineral wool be raised slightly from the roof so water going down the flashing won't wick in from the bottom? I know mineral wool is supposed to be hygrophobic...


Asked By Esther Streusand | Aug 8 16
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