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!

15 Answers

Wood floor underlayment over radiant heated floor


I am building a 2 story house wood frame house(with basement) that is heated with radiant hot water system installed in the floor.

The joists have been blown in with loose fill cellulose (for both sound and to keep the heat up) and a plywood floor is on top of the joists. R5 foam board is installed on top of the plywood and the PEX tubes are installed to the foam board. They will be pouring a self leveling concrete on top of the PEX and then gluing down engineered wood floors.

Asked By Howard Klein | Mar 5 14
6 Answers

Running PEX in-floor in addition to baseboard

I'm building a new wood frame home with hot water baseboard heating in climate zone 6. The bathroom will have tile floors and I was thinking of using some electric resistance heat under the tile along with a baseboard hot water radiator in the bathroom. These electric systems are not inexpensive to install or operate so I am now considering simply running loops of Pex (the supply line to the bathroom radiator) between the joists to keep the tiles warm before the water in the line gets to the baseboard radiator.

Asked By George LaLonde | Mar 2 15
4 Answers

Multi split with ceiling fans?

I am looking into a multisplit heat pump system for our deep energy retrofit project. We are used to leaky homes with ceiling fans in all bedrooms while sleeping. We find the moving air to be very comfortable while sleeping. In fact we noticeably miss the fans when traveling even when there is a dedicated Hvac like in a hotel room. In general, is the modern usage of the term 'comfort' (meaning stable temperature and humidity) consistent with our desire to feel the lightly moving air when sleeping?

Asked By alok khuntia | Feb 27 15
6 Answers

Air-source heat pump vs. AC/furnace

I am contemplating some different HVAC options in Connecticut (zone 5). I currently have an 80% efficiency Carrier Infinity NG furnace (8 years old) that can be paired with a Carrier Greenspeed heat pump. I can do that for $11,400 before incentives, or replace my existing and dying 10 SEER AC unit with a new 16 SEER for $8,000.

Asked By Anthony Kane | Feb 24 15
2 Answers

Load rating for 2x4 by 2x6 post

We are adding a second floor over living area, the room size is 35' x 18.5'. We have divided the room into three sections with a two support beams in middle of the 18.5' section. What would the load rating be for the post if it is made of 2- 2x4 and 2- 2x6 hollow middle?

Asked By Tim Eicher | Feb 24 15
26 Answers

Most cost-effective whole house ventilation solution for Massachusetts?

I am building a Tier III home on Cape Ann and will be having a single minisplit heat source for my open kitchen/living/loft area with 2 bedrooms and a bathroom also downstairs (896 sf downstairs). I have read all the discussions regarding exhaust only ventilation vs HRV/ERV. There are many HRV systems out there at varing costs. I am trying to find the most decent cost effective solution to whole house ventilation. I was considering Lunos fans but have heard that white noise could be an issue. I am looking for quiet and also cost effective to run over time as well.

Asked By Victoria Williams | Feb 19 15
3 Answers

Indoor air quality in a ventillated NZE house when power goes out

We live in a NZE house of about 34795 ft3, and it has a ACH50 of 0.46 - the actual number was 269 cfm @ 50 pa. The Zehnder ventilation is set to 144 CFM. 4 bedrooms 3.5 baths.
If the power goes out, do we need to worry about suffocation? I would prefer not to open windows, to maintain the heat in the house for as long as possible. - the power goes out in the winter, usually. Has anyone done any studies on the indoor air quality in such a situation?

Asked By David Hobart | Feb 16 15
12 Answers

Makeup air in all electric home?

I have read a lot of blogs and questions that, quite reasonably, recommend makeup air for kitchen exhaust fans in tight homes. The use of these fans can cause backdrafting in combustion appliances. But what if the home does not have any combustion appliances? We typically design very tight homes, around 1 ACH(50) with no combustion appliances. We use heat pump water heaters, Mitsubishi mini splits, and electric condensing dryers. We also use Induction ranges and cooktops. No fireplace. We tell our clients that if they want a fireplace, they can have one...outside.

Asked By Rob Shearer | Feb 11 15
17 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
9 Answers

Ducted HRV, Lunos e2 or Extraction only

Thanks in advance for your knowledgeable advice. I understand just enough about air sealing, heat recovery, and ventilation to be completely confused as the best way to go about ventilating the house I am currently building. This house is a very small (700 sq ft./64 m2) open plan, one bedroom/one bath strawbale house with a small loft and a simple raked ceiling. I am attempting to build it very tight, but won't have actual figures on that until after the first coat of render and blower door test in April or so. I do need to consider electrical runs and potential ducting now.

Asked By Enga Lokey | Feb 1 15
Register for a free account and join the conversation

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