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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.


In Mechanicals | Asked By Keith H | Oct 16 14
6 Answers

Which point-of-use tankless water heater should I get?

I live in Cambridge Massachusetts. I need a point-of-use tankless water heater for 1 bathroom sink. I will use the hot water for about 5 minutes at a time. What is the correct size? Can you recommend a brand?

In Green products and materials | Asked By Eve Schlapik | Jun 9 14
6 Answers

"Venstar Free Cooling"

I saw this in the instructions for a Venstar Thermostat, which is a fresh air intake to provide "free cooling" when the outside temp drops. The main return would close and the fresh air open with only the blower running.

I suppose that the fresh air intake should be the same size as my normal return (18") for the outside air to do anything right?

the drawing also shows a barometric damper at the return grille for pressure equalization.

Would this save me money in Sacramento CA? What are your thoughts...


In General questions | Asked By Manny Manuel | Oct 15 14
1 Answer

Vented roof insulation

For a vacation home in a 5b zone, does it make sense to put exterior rigid insulation (1" xps) under a standing seam metal roof? This will have a vented attic with no mechanicals up there. I anticipate blow-in on the ceiling deck.

In Green building techniques | Asked By Robert Holland | 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.

In Mechanicals | Asked By Gregory Worrel | Jun 1 14
4 Answers

Basement ceiling insulation required by code — but what about the basement door and stairwell?

Seems like a huge thermal hole in the basement ceiling. Code requires R30 in zones 4 plus for unconditioned basements. What about the bottom of the stairs (to 2nd floor) and exposed stairwell walls? People typically just use an interior door to the basement, right?

In Building Code Questions | Asked By Dwight Harris | Oct 15 14
3 Answers

Unusual thermal envelope intrusion at roof-penthouse


I've discovered that the ~1987 penthouse addition to my house is partially outside the roof thermal envelope . Since it is attached (naturally) to the remainder of the house it compromises the performance of the whole house.

In a nutshell:

In Energy efficiency and durability | Asked By Keith H | Oct 14 14
27 Answers

My husband and I want to build an efficient house

My husband and I want to build an efficient house. The only problem is we are on a very tight budget.

In General questions | Asked By K Nuss | Oct 11 14
10 Answers

Choose between more/better insulation, or heat pump?...

Last year we had an energy assessment performed in our 1880's home and were recommended several options. We opted to first pursue air sealing in attic with 20" of blown in cellulose. This made quite a difference both in comfort and heating bills.

Our remaining recommendations:

1 - Insulate walls with dense pack blown in cellulose.
2 - Insulate crawlspace (closed cell spray foam).
3 - Replace 4 windows original to house (drafty!!)
4 - Install high efficiency air source heat pump.

In Energy efficiency and durability | Asked By Christian Rodriguez | Oct 9 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.

In Mechanicals | Asked By timothy flynn | Oct 15 14
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