Community: Mechanicals

[Click map to enlarge]

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

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

What's the best way to integrate rain water to a condo system?


First of thank you for having such a wonderful forum to share infornation on. I have found this place very usefull in the past.

To my question: im designing a 7 story medium sized condo that will house 6 families. Im thinking of integrating rain harvesting to the building as we some times get droughts and i hate to see all that rain water go to waste. I think it should be regulation to have some sort of backup water sytem just incase the mains dry up. But for now will just be using rain water for the watering closet.

Some numbers:

Asked By Osman Naskali | Jan 24 15
3 Answers

Wall vent vs. roof vent

We are installing a custom wood range hood and can't decide between venting through our wall or heading through the roof. The duct is 6" round. Going through the roof the run would be about 3-4' straight up. Roof is pitched about 5-12 and the vent cap would land right around 30" from the eave.

The range sits on an exterior wall, so heading though the wall would give the run a 90 degree turn and about 2' of ducting. The siding is 4" lap fiber cement. Any pros or cons or suggestions to persuade me one way or another?

Asked By Matt Cibula | Jan 25 15
22 Answers

Best HVAC for a 1,100 sq. ft. passive solar house at 46 N latitude?

We are building high-performance, all electric, 1,100 sq foot passive solar home in cold weather winter climate with hot, humid summers. Slab on grade. Exposed concrete floor as thermal mass. Natural gas is not available. Winter temps infrequently reach -20 to -30 degrees range in December and January. We will use modeling to size heating and cooling system. We will have two bedrooms, open living, dining, and kitchen (primary solar gain area). In addition, there will be a full bath, 1/2 bath, mudroom, and mechanical room. Heating days the last 3 years: 7,065; 8,980; 9,799.

Asked By Randy Bunney | Dec 26 14
15 Answers

New study on heat pump water heaters' reliance on the home's heating system and viability of ducting the HPWH

This came out sometime in 2014 and I haven't seen anything about it before.

The points that I took from it are:

  • The heat "stolen" by the HPWH is less than expected, at least when located in a room that is partially on the exterior surface of the home.
  • Exhausting the HPWH to the outside without also ducting its intake can have a harmful effect on the home's heating energy use, since it needs makeup air, which comes from outside and can be even colder than the output air of the HPWH.
Asked By Nick Welch | Jan 9 15
3 Answers

What is the calculation method to determine the actual BTUH output of a hydronic radiant floor?

We are looking for a mathematical calculation for determining the actual btu output of a hydronic radiant slab floor in a basement. Any assistance is greatly appreciated.


[The author of this question has asked for his name to be omitted.]

Asked By GBA Team | Jan 16 15
6 Answers

Minisplit setup for New Jersey, 750 sq. ft. house over crawl. Bouncing my HVAC contractor's plan off you guys.

The short. I have a 25x30 rancher over a currently vented crawl. It sets almost perfectly south facing on the 30ft long side. No tree shading on south or west. Deciduous tree shading in the east and some on the north side. It's two bedrooms one bath, kitchen and living room. Standard stick frame 2x4 construction and vinyl siding. House was built in 1963 in a post WWII development.

Bedroom1: 10x12
Bath: 5x9 rough estimate
Kitchen: 9x11
Living: 14x14 rough.
Short hallway off living room with bedrooms at the end: 4x7

Asked By Lance C | Jan 16 15
16 Answers

Mitsubishi mini split behaving very differently with external thermostat vs. without

I am able to monitor my home's electricity use and I always thought it was a little weird that my Mitsubishi FE18NA heat pump seemed to constantly be spiking up and down, considering that the whole idea of the inverter-driven compressor is that it can run smooth and steady... fast forward to yesterday when I received my MHK1 thermostat and hooked it up. Suddenly, the power usage was steady as a rock.

Asked By Nick Welch | Jan 6 15
1 Answer

How to optimize HVAC ducting

I will be building a new home in Idaho in an area not serviced by natural gas. Most new homes there use electric heat pumps. In brief, super insulated and well sealed 2400 SF with 900 SF attached garage, 750 SF bonus room, conditioned crawl space, vented attic. I’ve never worked with heat pumps or ducting before. I’m uncomfortable turning the design over to an HVAC contractor without specific instructions. Two have told me the air handler will be placed in the garage and return will be through the (unconditioned) attic.

Asked By Dick Lowman | Jan 14 15
12 Answers

Can I make mini splits more efficient at extreme temperatures?

I renovated a home in northern New Hampshire with meaningful air sealing and additional insulation. I installed Mitsubishi hyper heat mini splits upstairs and down, but have baseboard and wood stove backups for when the temperatures drop below 20f and the mini splits need help. Overall, I am happy.

My question is about the outdoor units. Below a certain outdoor temperature the mini splits lose some energy efficiency.

Asked By Phillip Roshak | Jan 14 15
2 Answers

New Mitsubishi Hyper Heat multi splits have finally arrived

I was having a discussion with someone on reddit and they mentioned having a MXZ-3C24NAHZ model recommended by a contractor, which I had never seen before. Googled it and, lo and behold, I find documents published just a couple months ago (like this one) describing a whole new line of Hyper Heat multi splits, sized from 20,000 BTU/hr through 48,000, and supporting 2 to 8 indoor units. HSPF rating is generally in the 9 to 11 range.

Asked By Nick Welch | Jan 13 15
Register for a free account and join the conversation

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