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21 Answers

Mitsubishi minisplits — horizontally ducted

Sorry - I blv I posted the same in another section. Please ignore this question if it's a duplicate.

We are not fans of ductless units. Therefore, we opted for the hidden horizontally ducted units that Mitsubishi provides. Unfortunately, all the Mitsubishi contractors we talked to have never designed a home with these type of units. Plenty of ductless experience.

Asked By Ismail Mohammed | May 21 16
3 Answers

Stand-alone infloor cooling system?

I live in northern Canada. It does not get hot very often, but when it does we can get 90-100F for a few weeks or even a month.

I've got full radiant heat system with 8" OC spacing for heat pipes, many zones and a very snazzy pump setup. I've also got 4 HRV's keeping the air moving.

The infloor heat works great, and I find it very efficient.

For the few months of the year where its hot out, the house can get hot. Depending on the room, it can become un-usable. This of course has to do with all the windows and the solar gain. Hey, I like a bright house :-)

Asked By Mark Helmrich | Aug 28 16
6 Answers

ERV and humidity

This is more for my own curiosity.

I've read that ERV's are generally suggested for warm humid climates and I've also read they can cause humidity levels to rise within a home. My understanding is that with an ERV some moisture is transferred from the stream that contains higher levels of moisture to the stream that contains less. Does the system medium look to balance the amount of humidity between both streams?

Example, Stream A is at 40% RH , Stream B is at 20% RH, ~10% is transferred from A to B where both end up at ~30% RH)

Asked By Chris M | Aug 25 16
3 Answers

“Smooth” flex duct

I understand that flex duct is bad in most situations--it decreases blower efficiency and just generally impedes air flow. That said, for a longish (25ft) run of 6" duct, I wonder if it wouldn't be okay to use one of the 'smooth wall' plastic ducts on the market (see http://www.flexaust.com/product/grass-collection-vacuum-hose/) for a good example of what I'm looking at. This would be in a relatively low-pressure type of situation (Minotair hybrid HVAC system installation).

Asked By Jonathan Nagar | Aug 26 16
15 Answers

Solar hot air preheat for HRV/ERV

Has anyone seen a successful approach to using a solar hot air collector to preheat the intake air for an HRV / ERV?

It would be fairly simple to bypass the collector when preheat wasn't desirable.

One major concern is regulating temperature so excessive heat doesn't compromise the HRV / ERV.

It seems like it could be an ideal way to temper incoming air on cold, clear Colorado days (climate zone 6B), and get a little extra solar gain.

Asked By Pat Kiernan | Aug 17 16
7 Answers

Why is my brand new HRV filled with water?

We did a DER in MA recently (complete September 2015). Part of the mechanical system design includes a Zehnder 350 that is designed to run 24/7 on medium flow to have sufficient air exchange. We have really high heat right now and high humidity. I noticed just now that it was making a strange noise. I opened up the cabinet (following the instruction provided) and found the right side (leads to the house air handlers) was full of water. There is a condensate outlet drain on the left but there is no way for water to get from the right to the left.

Asked By Erica Downs | Aug 12 16
3 Answers

Central Fan vs. HRV

Hi all another question.

Background: I live in Minnesota (6B on the climate map) and I have a 3 year old house with bath fan exhaust only. There are 3 bath fans on the second floor that run constantly. House is about 3800 sqft now and will be almost 5000 sqft when basement is finished. We have been running the furnace fan constantly recently to keep the house even in comfort, I'm experimenting with "circulate" vs. always-on. Furnace is high efficiency but with an old school motor, not ECM. I don't see us proactively changing the furnace in the near term.

Asked By Ben H | Aug 20 16
2 Answers

ERV with dual ECM motors and good controls

Is there anything else besides Zehnder (a bit pricy, but quality supposed to be great) and Recouperator (looks dated and also pricy considering accessories) on the ERV market that would fill below requirements:

1. 2 ECM motors.
2. Economizer or free summer cooling (assuming humidity levels are not crazy)
3. Being able to set it to slight positive pressure (and ramped up speed to get to it while using clothes dryer and wood burning stove)
4. Controls good enough to do #2 and #3, optionally in conjunction with existing 3 zone Prestige IAQ and HZ432 ran system.

Asked By Nick Zees | Aug 12 16
2 Answers

Moving from exhaust-only to an HRV - outside venting question

Hi all, appreciate any help you can give.

I live in Minnesota (6B on the climate map) and I have a 3 year old house with bath fan exhaust only. There are 3 bath fans on the second floor that run constantly. House is about 3800 sqft now and will be almost 5000 sqft when basement is finished.

I'm thinking about switching to a HRV while the basement drywall is still open and shutting down the bath fans. In mechanical room HVAC is high efficiency so plumbed intake and exhaust. There is a 6 inch flex fresh air in the mechanical room seemingly just for the water heater.

Asked By Ben H | Aug 19 16
62 Answers

Questioning my logic...GSHP, ASHP, radiant?

I'm in the planning/almost ready to break ground stage of a new home and I'm beginning to question my sanity when it comes to figuring out the right approach for heating & cooling.

The home is:
North end of Climate Zone 5
Main Floor: 1700 sq ft + 1000 sq ft garage, vaulted ceilings through much of it
2nd Floor: 1100 sq ft (2 bedrooms, 2 baths, living room) primarily over the garage
Basement: 1700 sq ft, partial walkout + 1000 sq ft shop under the garage (separated from the rest of the basement)

Walls: R30+ (2x6, 2" XPS outside, 2lb SPF for sealing + 1/2lb SPF for cavity fill)

Asked By Dave De C | Jul 16 16
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