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11 Answers

Minisplit for a small room

I'm considering a mini-split install in our house. I'm in Austin TX, so it's a climate that requires significant cooling. I have calculated loads and I have questions about what happens if one has a mini-split running in a low load room. It's a child's bedroom and the doors are closed all night.

The room has internal walls on 3 sides and just one 3x5 window. Currently the load calc shows it at about 3300 BTU (of course that is at design temperatures of nearly 100°F and 72°F inside).

Asked By James Howison | Apr 18 18

5 Answers

Frustrated with local HVAC contractors - should I outsource the design?

Hi everyone. We're building a pretty large house here in the SF Bay Area, and having a devil of a time trying to find an HVAC contractor who'll actually design things using calcs and not eyeballing it. When I finally got one to do a manual J, he had to quit the program due to a family member with a terminal illness.

Asked By mike myers | Apr 18 18

8 Answers

Furr-UP instead of furr-down to include ducts in the envelope?

Hi all,

I'm building a new home in south Louisiana and I've been lurking here for a few week soaking up some energy efficiency building techniques.

One of the biggest points I see on here is to include the HVAC system in the insulation envelope. But, that isn't standard practice in Louisiana for new construction ( as in, NO ONE does it in my area). I get the deer-in-the headlights when I even mention a closet unit with ducts installed in furr downs. This also goes for Framers and Home Designers

Asked By Jiggernaut | Apr 18 18

12 Answers

Mini Split sizing feedback

Howdy all wanted to gauge your thoughts on Mini Split sizing

House facts:
- Built in 1955
- 1008sqft feet
- Single level ranch
- Poured concrete foundation with full basement, unfinished.
- First generation Corning/Owen Fiberglass batt insulation in walls, probably r-11
- r-30 batt insulation in ceiling installed within the last decade..
- White Cedar siding, laid over some kind of particle like panel material coated in black as sheathing.
- Multiple single pane windows with older retrofitted storm windows, two newer double paned windows.
- Ellenville, NY

Asked By evantful | Apr 14 18

6 Answers

Too small a boiler

Can a boiler which just meets your heat loss be too small to use an indirect water heater? Indirect WH seem to rely on significant amounts of boiler to do the job. If you are at design outside temperature, do you have to make a choice between hot showers or warm house. Is there some point were a standalone water heater is necessary and what is the effect on overall energy use. Oil is my fuel of choice if that matters, no gas.

Asked By Jonathan Blaney | Apr 12 18

31 Answers

Heat loads and mini-split.

Hi
So had my heat loss calculations done on the new build, and would like some input from people regarding what mini-split they would recommend and placement of the heads, I’m in Zone 6 and the house is single storey with a walk-out basement, total square footage with both floors is 4400.
The following is what they came up with: Main floor Htg load 11889 Btuh, Clg load 12613 Btuh
Walkout Basement Htg load 10792 Btuh, Clg load 2658 Btuh
Total : Heating Load 22681 Btuh
Cooling Load 19582 Btuh

Asked By Dave B | Apr 5 18

2 Answers

De-superheating for dhw

I see a product from Olive Tree Energy called a ZeroEnergy Water Heating System. Any experience with these or similar products. Is it a good concept? Maybe one of these added to an indirect tank and electric backup so you can turn the boiler off for the summer.

Asked By Jonathan Blaney | Apr 13 18

14 Answers

Minisplit sizing dilemma — to replace oil furnace

I love the GBA website. Thanks for so much good information.

We're in the planning phase for replacing the 31 year-old oil furnace in our 1200 sq. ft. house in Portland, Oregon (climate zone 4C) with a mini split heat pump. The heat pumps we're considering is the Daikin FTQ18PVJU or the FTQ24PVJU.

The house was built in 1960 and is 3-bedroom, 1-bathroom, 2-story, slab-on-grade construction. Windows have been replaced with double-pane, low-E windows and modern solid-core wood doors with tight weatherstripping but those are the only energy improvements the house has installed.

Asked By Oregon1859 | Feb 25 18

6 Answers

flex duct material for ventilation

It was recommended to me by a couple of independent sources to include a short run of flex duct between my HRV and the supply and return manifolds, for noise control purposes. The idea is to decouple the unit from the ducting as a means of reducing vibration transmission. I've looked at several options:
1. Vinyl dryer duct. Very flimsy, has a pretty nasty smell to it, probably not a good choice from an air quality standpoint.
2. Foil dryer duct. Also very flimsy.
3. Semi-rigid aluminum dryer duct. Seems too rigid to actually achieve the goal of decoupling.

Asked By Trevor Lambert | Apr 11 18

3 Answers

ERVs and VOCs

Quick question: One of the advantages of using an HRV or ERV is to exhaust household air that may contain off-gassed VOCs. ERVs exchange both heat and some moisture between the incoming air and exhaust air.

Does it also exchange some of the VOCs, so that the incoming fresh air may contain a portion of the VOCs we are trying to exhaust out of the house? I'm not sure how it could exchange moisture, but not gaseous chemicals.

Asked By Debra | Apr 10 18

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