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0 Answers

Making sense of 1st month mini split heating data

I have 4 Fujitsu mini splits (non xlth) hooked up to (2) 24k condensers. They were primarily for AC but I'm trying to reduce usage of my aging 199k/152k steam boiler while the temps are relatively mild (Boston). Right now I'm using a 12K head per condenser, per floor, so 2 total. Dana had some good advice as the min modulation range was about 6200 BTU/hr per unit, and to run both units, so this weather seems to be the sweet spot for efficiency and load.

Asked By kjmass1 | Dec 12 17
3 Answers

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
11 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
0 Answers

Workshop w/ Dwelling Above - Heating Advice


Asked By user-6964558 | Dec 12 17
7 Answers

Brick house insulation


My situation: I have a brick house, that initially had plaster and lathe walls. With the floor joists supported by inner wythe, and the joist ends embedded in the brick. I removed the plaster and restudded the walls with 2x4s.

My concern: On the lower floor, I insulated the stud bays with batt insulation. I thought this was a good thing, however, after reading your article I think I may have been mistaken.  I am beginning work on the second story and don't want to make matters worse.

Asked By 3rd Little Pig | Dec 9 17
0 Answers

Horizontal ducted mini split ducting

I plan on using a Mitsubishi 12K BTU horizontal ducted mini split, Model: SEZ-KD12NA4R1.TH to provide both heat and AC to two second floor bedrooms. The unit would be inside the building envelope in a dropped ceiling in a hallway between the bedrooms. I'm having trouble determining what adequate ducting would be.

The Mitsubishi submittal document has graphs for different static pressure that relate to CFM but I struggle to relate this to a duct design.

Asked By jim sweazey | Dec 12 17
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
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
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