Community: Mechanicals

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4 Answers

Open-air barn

We are designing an unconditioned "party barn" in Central Texas for occasional gatherings for groups of various sizes. The barn has about a 1,400 sf footprint -- 1,400 sf at the ground floor then there is a loft that is about 200 sf. We have Big Ass Fans for air movement but would like to add an attic fan to exhaust the warm air that will build up in the loft/attic space. How do we calculate the amount of CFM that the fan should be moving?

Asked By Heather Gayle Holdridge | Jun 26 15
2 Answers

California heating question

I have a 1910 craftsman home in the Bay Area where we might need cooling 4 or 5 days year and it typically does not get too cold. We are redoing the basement (seismic) and attic (new roof, beefed up framing) and will install a solar PV system. I will most likely go to a heat pump water heater and a new heating system (presently have floor furnaces). I am thinking about a mini split system or a ducted heat pump system with the ducts in the attic. What are the advantages and disadvantages to both? The house is 3 bedrooms and about 1800 square feet.

Asked By rob manheimer | Jun 29 15
1 Answer

OTR Microwave as range hood in tight house?

I'm looking at a range hood for ventilation in a new, tight, house build. I've read the articles like:

which talk about buying a range hood with a small exhaust fan. Martin recommends 150 CFM to 250 CFM with a tight house.

Asked By Nick Hall | Jun 26 15
29 Answers

Radiant floor heating using heat pump?

We live in a Zone 7 area and are building a one story 2000 sq ft on a slab and have decided we would like to heat the house with in-floor radiant. We have been told by HVAC specialists that the best solution would be geothermal, followed by hot water heat pump, electric hot water, then forced air heat pump and electric radiant. We don't have natural gas so that is not an option. Geothermal is out as it is nearly three times the price of the other solutions and this is a retirement home.

Asked By John Ball | Jun 19 15
4 Answers

Supply ventilation - energy use impact

I downloaded BEOpt and EnergyPlus and have been experimenting. Some of the outputs are surprising at first but make sense when I think more deeply, However, I have not been able to make sense of the results I am getting for different ventilation options. I am trying to determine if there is some physics advantage to supply ventilation or whether the results I am getting are modeling errors.

Asked By Reid Baldwin | Jun 22 15
11 Answers

Heat loss calculation and minisplit location questions

I am building a modular energy efficient house in N. Reading, MA. The modular company PBS has a lot of experience building energy efficient homes which is why I am surprised at their heat loss calculations. The house is 3860 sq ft not including the walkout unheated basement. PBS uses the ADA in their building method and the other house details are as follows:

House is oriented northwest-southeast
Paradigm Triple Glazed Windows U-.21 Innie
R-10 under slab
R-20 on front and side concrete basement wall, back and garage are the same as above grade

Asked By Arthur Ledoux | Jun 21 15
3 Answers

ERV / HRV Details

The more I read both here in discussion forums and in articles, the more I ponder various concepts, and the more perplexed I end up. I'm a homeowner undertaking a gut-renovation on nights/weekends/holidays. I'm trying my best to balance idealism and the realistic necessities of my budget.

~2000 sf house in Southern CT; CCSPF insulation throughout; Hydro-Air HVAC system. I'm pretty well convinced that an ERV is the correct choice.

Asked By Matthew Kreuzkamp | Jun 22 15
3 Answers

Minisplit choices

I am looking to replace window ACs with split units but am running up against a common problem - multiple small rooms that each need their own cooling, but using individual heads will result in excessive cooling capacity and the problems it brings with it.. 3 small (2x 10x12, 1x 10x20) bedrooms, living room , and EI K all need cooling. Metro NYC area.

Asked By Richard Jackman | Jun 22 15
7 Answers

Air source heat pump water heater in a small mechanical room

I am building a 2-unit addition to a duplex in Portland, OR, resulting in a 4-plex. The new units will be largely separate from the old, and will be built to PH-like standards (very tight air barrier, heavily insulated). With an eye toward economy, I am thinking for the 2 new residences to share a mechanical room. In this mechanical room would be water heater(s) for both new units, along with an HRV (likely Zehnder 550) serving both units.

Relevant plans and considerations:

Asked By jonathan nagar | Jun 15 15
1 Answer

Mini split condensate - dense pack lesson learned

I built a pretty good house last year, heated and cooled by a 12k btu Mini Split on 1st floor and 9k btu Mini Split on 2nd floor. Toward the end of summer last year our first floor unit was not draining condensate then after partially insulting our basement ceiling with dense pack cellulose, our 2nd floor unit was not draining at the start of this summer. Long story short, after investigating many ideas to the root of the problem, we just recently discovered that the flexible condensate line was pushed around when I dense packed basement ceiling.

Asked By Christopher Vernott | Jun 17 15
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