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42 Answers

Why must HVAC decisions be so complex? (Or... Is geothermal worth it?)

In another thread, my choice for HVAC was appropriately questioned. The system seems inordinately complex, costly, and convoluted. At least, on the surface. But digging deeper, the reasoning behind the design becomes clear. But, does that make it right? Is this the best HVAC design, or is it redundant and wasteful?

Here are the pertinents:
• Climate Zone 6
• 2700 sq. ft. finished space in story-and-a-half (bungalow style) house
• 2000 sq. ft. unfinished basement (future completion for aging parents)
• 4 Bdrm, 3 ½ bath house
• Tight, highly insulated home

Asked By Kent Jeffery | Apr 16 14

1 Answer

Ductless Mini Splits & Cassette Units

Are the ductless minis that utilize a cassette unit vs a wall unit, less efficient?
Are there any drawbacks to a cassette unit over a wall mounted unit?
Lastly, can a cassette unit be mounted on a wall or is that not a good idea?

Asked By Peter L | Apr 19 14

11 Answers

Is a fully dedicated duct system for HRV truly the best option?

So, I’ve been researching the proverbial pee-pee out of this question: dedicated ductwork for my HRV or simplified installation? Here are the pertinents:
• Climate Zone 6
• 2700 sq. ft. story-and-a-half house, along with a 2000 sq. ft. unfinished basement
• 4 Bdrm, 3 ½ bath house
• Double stud walls, spray foamed exterior sheathing and cathedral ceiling, very “tight” and efficient house planned.
• Geothermal ground source heat pump, with gas furnace back-up (Xcel Energy “dual fuel” program allowing electricity to be purchased at 40% rate for geo.)

Asked By Kent Jeffery | Apr 15 14

4 Answers

Mechanical Ventilation in a Tight, Permeable House

Ok, I am going to thoroughly expose my lack of knowledge with this question (no claims to any expertise on my part), but I'm hoping that some of the experts here can comment on something I am thinking about.

Asked By Stephen Youngquist | Apr 16 14

10 Answers

ERV or HRV with these humidity numbers? Also best HRV brand?

I have a humidistat sitting in my house the last few years, and have taken notice of the RH%.

I am concerned that an HRV will dry out my house too much. Location is Toronto which has cold winters (down to -18 celcius) and summers up to 30 and 35 celcius humid

With a forced air system with a humidifier installed, we go down to about 16% humidity in the winter on the coldest days. typical is around 20%-24% . In the summer we are at about 50-54% ish.

with these numbers would an HRV make it too dry, or would the numbers typically be affected only slightly?

Asked By cory b | Apr 13 14

1 Answer

Lunos eGo Now Available

Has anyone seen a review of this new HRV?

http://www.foursevenfive.com/index.php?main_page=product_info&cPath=70_7...

Although it is rather expensive, installation is dead easy and mechanically it is exactly what I've been waiting for for 35 years.

Consider this... when the occupants are active in the main living area, exterior doors probably get opened and closed a few times every evening bringing in significant fresh air. (This is an impossible calculation, but could be verified through measurement)

Asked By Kevin Dickson, MSME | Apr 11 14

4 Answers

Is 170 watts normal for compressor heat?

Just put a Mitsubishi MUZ-GE24NA in my home. I checked the standby loss with the inside unit turned off and found that it was drawing 170 watts. I called Mitsubishi and they said it is the compressor heater and it is always on any time it is below 66 degrees.

Needless to say I'm very unhappy to have put in something in that will use around $15 dollars a month before it even produces heat.

Has anybody else had issues like this or do I have a defective unit?

Asked By Paul Lennon | Apr 8 14

1 Answer

Lineset losses?

Has anyone tried to quantify heat loss through the outdoor parts
of typical heat pump lineset installations? Does it matter much?
It occurs to me that some token amount of insulation is applied
there, but is it sufficient? Especially on the vapor line, which
runs pretty warm in heating mode and the farther the lineset goes
before coming indoors, the more it's exposed to a high delta.

Trying to ballpark it, assuming typical pipe insulation with about
a 1.5" outside diameter and half an inch thick, what is that stuff
usually, about R-3? Assume a ten-foot length running outdoors to

Asked By Hobbit _ | Apr 2 14

1 Answer

Need impartial help sizing and choosing a brand of minisplit-ductless A/C

Let me thank you in advance for your advice.
We're putting a minisplit ductless system into 3 rooms. 1 compressor and 3 heads.
I've gone to 3 contractors and each has given me different information. 2 of the contractors use Mitsubishi and the third uses Fujitsu. Needless to say they all include heat pumps.

The house is a 1929 stucco structure

1st room is a bedroom on second floor
14'3"x 10'6" x 8' ceiling
exterior wall on one side and one end
windows:
4'8"x2'9"
18"x 2'9"

Office on third floor (no attic steep pitched roof)
9'9" x 10'8" x 8'10" ceiling

Asked By jon keller | Mar 31 14

4 Answers

Can someone tell me a few minisplit models that work exceptionally well in the colder climates?

Climate zone 6.
Approximately 1000 square foot area. Will be very well insulated. R40 floor, R60 or better roof, R30 walls with well detailed air sealing. Approx 76 sf of triple glazed windows.

The floor plan is very open, so I'm hoping one unit will be sufficient, with some electric baseboard supplemental heat in strategic areas.

This winter was horribly cold, with many days below zero, but I wouldn't call that the norm. The coldest day was approx -18 below for the low, and approx -8 below for the high.

Asked By Rick Van Handel | Mar 26 14

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