Community: Mechanicals

Q & A Instructions

[Click map to enlarge]

The GBAGreenBuildingAdvisor.com 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!


6 Answers

HVAC sizing disparity relative to HERS report

My HERS rater shows heating load of 39,500 Btu/hr and a cooling load of 22,600 Btu/hr on a high performance house I plan to build. This includes 1000 sq ft of basement, 2500 sq ft on the main floor and 800 sq ft in an office/loft area. R40 ceiling, R20 walls, R5 basement and crawlspace wall insulation plus serious air sealing (3 ACH or less).

The HVAC quote shows no system in the basement (it will be finished by me after construction), 3 tons on the main floor and two tons for the loft with all duct work in the conditioned space.

Asked By Norman Bunn | Sep 20 17
6 Answers

Make up air and multi zone sensor

I do instal 600cfm rangehood in my kitchen. Vented outside of course. I have also motorized damper supplied by the manufacturer and it will be installed on the dedicated make up air duct being controlled by the switch on the hood. This part is clear. What is less understood is the question of preheating this make up air supply. The climate is cold up here and air, if not preheated, will mess up the whole system. Of course, company like Fantech offers elegant solution but... what if... Ecobee makes a thermostat with multi zoning temperature control sensors.

Asked By D.Kits | Sep 17 17
45 Answers

Zone 6b, Mass. Coast, mini split / Fujitsu?? Mitsubishi?? size?

hello,
I live in a coastal town north of Boston. My 1200 square foot house (600 upstairs, and 600 downstairs) is heated via electric baseboard heating. I never go above 60 degrees in the winter and still spend over $400 per month and this is with each room with its own thermostat and me turning them all down to mid-50's when no one is around and only turning up those rooms where we are. It is ridiculously cold in my house in the winter.

Asked By indoorsy | Sep 5 17
19 Answers

Pros and cons of gas vs. electric for DHW, cooking, and in-floor radiant heating?

We are building a 2000 sq.ft. Single story, 'pretty good house' in zone 6B in Colorado in a small town with both reliable electricity an natural gas. We are weighing the pros and cons of gas powered v electric powered system for DHW including the infloor radiant heating. If we set aside the issue of fossil fuel use, what are the pros and cons of each? Thanks in advance.

Asked By user-6885857 | Sep 10 17
8 Answers

SIP house — Backup heat source?

I am going to be building a 26' x 32' SIP enclosed house (6 1/2" Walls and 12" Roof) that will be heated with a Ductless MSP (1 outdoor unit and 2 indoor heads). My coldest day requirement will be around 17k BTUs per hour. The design temp for coldest temp is -15. I know I will need a backup system for when the Coefficient of Performance drops down... I have tentatively designed for a woodstove as backup but I really would rather avoid it.

Asked By John Brown | Sep 16 17
3 Answers

Radon mitigation with sealed crawlspace and partial walkout basement

Does anyone know of a resource that addresses radon mitigation for a foundation area with a sealed crawlspace and partial walk-out basement on new construction in Zone 3A?

I am assuming the crawlspace and basement mitigation systems can share an exhaust pipe and I have a good understanding of the under slab portion for the basement. So, what is the best method for the crawlspace?

Asked By Norman Bunn | Sep 10 17
13 Answers

My HVAC guy disagrees with PH Planning Package

The Passive House Planning Package indicates that the heat load for my house should be 7,722 BTU/hr (4.4 BTU/hr-sqft, and the cooling should be 3,573 BTU/hr (2.0 BTU/hr-sqft).

I gave these numbers, and the entire PHPP file to my HVAC person. He was dumbfounded by the low numbers and ran our plans through a detailed Manual J calculations. Now, he admits that he cannot account for the superinsulated slab, but he came up with much higher numbers.

The quote is for various versions of a Carrier 38Mxx / 40xxxx (3 ton heat pump. So much for heating the house with a hair dryer.......)

Asked By Steve Young | Sep 13 17
3 Answers

Mechanical ventilation

Reaching out for some input on mechanical ventilation. We are building a new house and like anyone else, we are on a tight budget. We have decided to have our HVAC system designed and sized properly and going to use the folks at Energy Vanguard for the design. For the ventilation, as much as we'd love to include that in the services invariably the recommendations would more likely than not be cost prohibitive.

Asked By Thomas Roberts | Sep 15 17
22 Answers

Solar assisted Heat pump vs normal air/ground source ? Home in Nova Scotia

I have been researching different heating techniques for a new build in Nova Scotia

Details
4 acres of land
On the ocean (Ocean side is NE- SE)
2 story home + Walkout basement
Main level: 1,600 sqft + 2 car garage (730sq ft)
Upstairs level: 1,050 sqft 3 bedrooms/2 bathrooms (550 sq ft less than main level due to open ceiling)+ loft on garage approx 600 sqft (potential 4th bedroom and den) 450
Walkout Basement : 1,600 sqft (10 foot ceilings) with windows on eastern and southern side

Asked By snarbs | Sep 14 17
8 Answers

HVAC - Continuous Operation or More Zoning

Should I run a ducted heat pump system with ECM motors continuously or go with a more zoned approach with the units coming on and off as needed?

Asked By Kevin Camfield | Sep 13 17
Register for a free account and join the conversation


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