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8 Answers

Calculating how much air needed to even out temps for minisplit

I'm building an 800sf 2 story house, R20 under slab, R40 walls, R60 roof, as airtight as possible, but likely just double pane windows (due to cost). 12% glazing, mostly on south side, w/ 4" slab on first floor. Using Marc Rosenbaum's heat loss spreadsheet, I get around 4000BTHU building load here in Portland Oregon at the 97% coldest day of 23F and a design temp of 70F, so a delta T of 47F.

Asked By Tom Frisch | Oct 23 14
6 Answers

Thermostats with radiant floor heating

I recently read an article comparing forced air and radiant heat energy use. The finding showed that the folk with radiant heat set their thermostats higher than for forced air. I hope that I am not being silly, but how can a thermostat on a wall respond to radiant heat? If one put a metal foil around the thermostat ,but let air flow occur, would the thermostat read a different number? I read in Mr Lyles masonry stove book that a cathedral that had radiant heating only had a 2 degree difference between the floor and ceiling (75 feet up).

Asked By Mike Legge | Oct 12 11
2 Answers

Rated output for electric radiant ceilings?

I've been searching the web for a rule of thumb to calculate the rated output for a 40 year old electric radiant ceiling system. Must be some rule of thumb like 10 btu per suare foot......but I can't find it.
Thanks

Asked By Walter Gayeski | Oct 17 14
2 Answers

Best integrated system for water heating and radiant floor heating?

I'm looking to remodel my home and install radiant floor heating system. Can anyone provide any information on good heat sources (boiler, water heater, etc) and system arrangement (direct, indirect, closed loop, etc). Is it okay to combine DHW with radiant heat or is there some over arching reason why they should be kept separately?

Home details: Just south of San Francisco, 2500 sqft, two stores, 5 zones, Warmboard S floor board, mostly covered with hardwood flooring.

Asked By Dmitriy Khazansky | Oct 17 14
3 Answers

Experience with Rinnai vent-free convectors?

Anyone used or have experience with Rinnai Vent-Free Convectors?

I'm a little baffled by this product. No ducts, no vents, nearly 100% efficiency. Relatively low cost, relatively low total load. Am I missing something here? It seems like the low load crowd would be all over these, as a backup heating up for high efficiency minis if not as a main line unit.

http://www.rinnai.us/vent-free/products

Asked By Keith H | Oct 16 14
13 Answers

Replacing a natural gas gravity furnace in an upgraded small older home

I am a regular reader here and have learned a lot on this site. Thanks to all who contribute.

I have been upgrading the thermal envelope in a 960 square foot house in Detroit, Michigan for several years. I have injected polyurethane foam in the walls, R60 cellulose in the attic after air sealing, 2" XPS on the basement walls, and 2" XPS in the joist cavities in the basement. The windows are single pane but with caulked in place storm windows.

Asked By Gregory Worrel | Jun 1 14
4 Answers

Sizing a minisplit for a 900-square-foot Chicago carriage house

I have a two-level carriage house (900 sq. ft. total). Brick structure, framed in with R-19 insulation, two levels, open loft style.

I'm wondering if the 12000 BTUH Mitsubishi MZ-FE12NA would be enough to heat the space, or should I go with the 18000 BTUH MZ-FE18NA?

Also, is there any reason why I should consider the Fujitsu minisplit too? I've had good experience with the Fujitsus in a warmer climate (than Chicago), but the specs on the Mitsubishi Hyper Heats seem hard to match in a Fujitsu.

Asked By timothy flynn | Oct 15 14
5 Answers

Islandable battery bank box venting options

Anyone out there have experience with battery bank ventilation in a tight house?

We're building a PGH in Climate Zone 4A. It's designed for net-zero, so we'll have a 6 kW grid-tied PV system. It will also have islanding capability (provided by a dedicated inverter and 12 kVA battery bank).

Based on a rough blower door test we are < 0.6 ACH50.

The battery bank will sit in the basement, which is conditioned space. I want to make sure we are venting the battery box in a safe and effective manner. As I see the issue:

It must vent hydrogen gas effectively
It must not backdraft

Asked By Daniel Ernst | Oct 12 14
13 Answers

Space and water heating for a micro-load house

I've been re-reading Martin Holladay's posts on water heating as I once again deal with a small-ish super-efficient house: 1900 ft2 with a heating load of less than 20 kBtu/hour. The homeowners have access to propane and electricity and here in MN, electricity is still generated by a lot of coal, although the homeowners are planning for a pv system.

At the moment I've narrowed heat/hot water system ideas down to three:
1. use a 6kW modulating electric boiler for space heat (hydronic radiant) and also to fire to an indirect tank for hot water. Also, use a drainwater heat recovery device.

Asked By Rachel Wagner | May 14 13
7 Answers

ERV or HRV that scrubs the incoming air?

Hello all, I'm planning a new home and need some help on a ventilation issue. A couple of my neighbors burn a lot of wood in the winter, so much that you smell like a BBQ pit after a few minutes outdoors sometimes. Is there any ventilation system on the market that would scrub incoming air--activated carbon maybe? Or can anyone think of way to alter ventilation ducts on a typical ERV or HRV to do so that is safe for the systems and for me?

Asked By Antonio Oliver | Oct 9 14
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