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!

17 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

Third-party filters for Zehnder HRV / ERV units?

Besides ordering from zehnder, are there any other filters available that will fit their units? It's not a question of price but more so of long term availability. If they go out of business will I still be able to source filters? I haven't had the chance to pull one out of the packaging and go down to the local HVAC supply house with a tale measure.

I'm an electrician and not an HVAC contractor so I don't understand if these are a common size/shape/build or totally proprietary.

Asked By Lance C | Aug 29 15
9 Answers

Minisplit or furnace?

Hi, I know there is lots of discussion about this; however, our proposed new construction seems to be in unclear realm of which to use.

Asked By Mark Buckingham | Aug 28 15
7 Answers

Include provision for future ventilation?

The second story of my old farmhouse is gutted. I am in the middle of running electrical, etc and getting ready to close up the walls. It doesn't need it now, but as I keep working, the house may eventually need a ventilation system. Should I include provisions now while the walls are open for a ducted ventilation system later? Is separate ventilation ducting overkill? What type/size of ducting is typically used for the application? Is it best to locate grilles in the floor or walls?

I have done a lot of reading on the topic but I would like some input others.

Asked By Brian C | Aug 21 15
13 Answers

Keeping HVAC inside conditioned space

We have just started construction on my new house. I want to keep the HVAC inside the conditioned space for energy efficiency. The crawlspace will be conditioned and we are using open web floor trusses on the second floor to accommodate the ducts for the second floor.

Asked By Michael Geoghegan | Aug 22 15
6 Answers

"Cycling" ductless mini-split

I'm working on my wife re: her dislike for the appearance of ductless mini-splits, but I have a question regarding their operation.

Asked By Brad VanVickle | Aug 23 15
22 Answers

Is it reasonable to use 3/8" PEX supply lines to all fixtures?

I am planning the plumbing system for my Net-Zero Energy home that is being built to Passive House standards. I will be using PEX tubing with a manifold system using home runs. I designed the house so that the bathrooms and laundry room are centrally located, making the supply runs pretty short. I want to minimize the amount of water and energy being used and low-flow fixtures provide plenty of water for my needs (2.2 gpm at sinks and 2.5 gpm for showers).

Asked By Gerald Blycker | Mar 11 14
3 Answers

Split air line set deformation question

Hello All,

I'm installing my my own split-air system with three zones. One is an 18k ceiling cassette that has a 1/2" and 3/8" line-set. Despite my best efforts, the 1/2" copper got deformed when making a corner. It's not kinked, exactly, but definitely deformed. So my question is, will it work with the deformation or have I botched the line-set, altogether? I've attached pictures.

Asked By Scott Mcllarky | Aug 20 15
11 Answers

Positive pressurized attic space for fire protection and summer cooling?

I have a 4 year old Deltec home in Central Washington State. Zone 5B. Deltec homes are essentially round houses that have a center cupola that is vented. (Deltec homes has a web site if you need photos) This house has 2 wings that were stick built on site. The wings have continuous soffit vents and continuous ridge vents. The ceilings between the conditioned space and the attic were meticulously sealed. I am attaching a photo of the cupola from Deltec's web site showing the vents.

Asked By Elliott Nelson | Aug 12 15
5 Answers

Pool solar panels: Will they naturally thermosiphon?

I have a 35,000 gallon pool with a south facing roof top right next to it. Solar panels would be a natural fit. BUT, the filter pump and mechanicals are on the opposite side of the pool. Before re-plastering when I first bought the house I installed 2 ea.1 1/2 ' PVC fittings on the house side of the pool and capped them off.
The question is, will I need a large, 1 HP pump to circulate water to the roof (15' head +-), will a small fractional HP recirculating pump work, or will the water naturally thermosiphon up and down?
I can see where any air leak up high would be a problem.

Asked By Richard Stutsman | Aug 11 15
Register for a free account and join the conversation

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