Community: Mechanicals

Q & A Instructions

[Click map to enlarge]

The web site has a wealth of articles on a wide variety of construction topics. Before posting your question, you may want to check out the articles on this page: How To Do Everything. You just might discover an article there that provides the information you seek.

Please register for a free account or sign in to ask and answer green building questions.

If you want to post a question, the usual rules of courtesy apply:
1. Be nice.
2. If you can't be nice, be polite.
3. If you can't be nice or polite — well, please be brief.

To attach a photo or illustration: Under the box labeled “More explanation,” look for the words “File attachments.” Click that, and you should be able to attach a photo.

Thanks for joining the conversation!

2 Answers

Whole house fan with conditioned attic?

We're building a house in the Northeast and the owner is insisting on a whole house fan in addition to central AC.
The attic will be a semi-conditioned space with foam insulation in the rafters. This means no outside air exchange.
Is there a way to put in a whole house fan and vent directly outside?
House is about 3000 sq ft.

Asked By Pete Dusenberry | Sep 28 15
54 Answers

Dare to DIY a mini split install?

Hi all,
Can editors step out from behind the curtain to ask opinions, too? I'm planning to redo my garage shop this Fall and although my primary heat for the space is a woodstove, I'd love to have some supplemental heating, and cooling in the summer would be great, too. I'm no schlep when it comes to remodeling work, but have never installed or seen a mini split install. Would I be a fool to try the install myself or have the kits gotten streamlined to the point that its basically plug and play, complete with factory-charged units and quick connect line sets, etc?

Asked By Justin Fink | Aug 22 13
26 Answers

Has anyone had experience with the Unico small duct system?

I was looking at the top finishers for the department of energy's "Race to Zero Student Design Competition" ( ) and found the winner used the Unico system. I recall actually being in a home in Chattanooga once 15+ yrs ago that I believe had one of these systems, but I really know nothing about them. With the problems associated with finding small enough systems for well insulated homes and cost effective systems...does anyone know if I should be looking at this as an alternative?

Asked By Andrew Bennett | Apr 29 15
0 Answers

Dettson furnace and air conditioner

Does anyone on this forum have experience with Dettson furnaces or air conditioners? They offer a line of furnaces, called Chinook, starting from 15K btu/hr. They also have central air conditioning compressors, called Alize, starting from 9K btu/hr. The Alize literature also quotes a heating range, so apparently they are actually heat pumps. The furnaces modulate from 40-100% of rated capacity and the air conditioning compressor modulates down to 25% of rated capacity.

Asked By Reid Baldwin | Sep 21 15
6 Answers

Mini-split final install Qs

Hello All,

The info I've found in other threads regarding DIY mini-split installations have been invaluable, and I am very appreciative.

I am now at the stage in my own, 3 zone, install that it's time to pressure test, evacuate, and release the 410a. I purchased pro equipment to do the job and I just have a few lingering questions I'd like answers to, along with any advice, before proceeding.

Asked By Scott Mcllarky | Sep 17 15
1 Answer

ERV - Sizing and location with wood stove?

With the tremendous assistance from all you folks, my Bozeman MT historic bungalow replica is well underway, my son and I have got the framing completed, the roof is on and the drain, waste, and vent are installed. It sits on a basement that equals the first living floor of 1,300 sq. ft., and then the two bedrooms upstairs add another 750 sq. ft. The air here is arid, can be hot in the summer an for a couple of weeks, damn cold in the winter. Due to the roof orientation, I've only been able to do a solar hot water system vs. solar electric.

Asked By Brian Martin | Sep 16 15
6 Answers

How efficient are horizontal axis washing machines? Really?

Since 2002 I have had 2 different high efficiency washing machines. The first failed within warranty and was repaired for free and at 7 years of age failed catastrophically. I got a new one and now it needs repair. These are high tech machines and I can't fix them myself. I am considering buying an old fashioned "new" , belt drive, mechanical timer, commercial, Maytag.

Asked By Steven McCarthy | Sep 9 15
2 Answers

Why would someone buy a heating (gas fuel) and cooling package unit?


I recently moved to CA and have started seeing a lot of homeowners installing heating and cooling package units, usually installed on the roof. These systems are gas-fueled, with a max AFUE of 81 or so. Why would someone buy one of these units instead of a full Air Source Heat Pump to do heating and cooling?

For example:

Thanks for your help!

Asked By Whitney Larsen | Sep 8 15
8 Answers

Any hydronic system controls with low standby electricity consumption?

I was feeling good about the changes I'm making to reduce the electricity consumption of my hydronic system: a Grundfos Alpha ECM pump that is consuming only 16 W when it's running, and Taco "sentry" zone valves that use about a watt when on. But I measured the power consumption of controls last night, and it can add up to almost as much as the pump: 3 W for an aquastat, 6 W for a Taco "switching relay" circulator control with one zone on, and 4 W of standby power for the 40 VA 120:24 VAC transformer that powers the zone valves.

Asked By Charlie Sullivan | Sep 2 15
2 Answers

Mini-split condenser on south side of house?

I'm in climate zone 2B. Winter nights drop into the 20s; days reach the 50s. Summer days reach 100 and cool to 70 at night. We get maybe a few inches of snow per year. The Manual J heating load for my house comes out to around 12,000 BTU, cooling around 6000. Would it optimize efficiency to place the outdoor unit on the south side of the house and shade it (with plenty of clearance) in the summer and expose it in the winter? (The south side is the best spot for other considerations particular to my floor plan.)

Asked By Jeff Cooper | Sep 5 15
Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!