Air Exchanger help

[justinjoyal]

Bathroom have odors and higher humidity -- you can't control the odors and the system will be distributing them to other parts of the house. You are also pulling air into the bathroom from the rest of the house -- typically in a cold climate you provide a bit more CFM to the bathroom to keep it warmer ... with continuous venting from the bathroom you are making it colder. It's a major complaint of the HRV/ERV use as bathroom vents. Does the same thing in the summer with AC. They are also marginal humidity controllers in many parts of the country -- the can only blend with what's outside .. this causes them to run longer. Liek i said a couple of times -- Fantech makes the best exhaust -- they run for 6-8 min and it's over.



The new HVAC systems eliminate most of the need --

My experience over the past 5 years with different houses using balanced, properly installed HRVs used as bathroom vents is consistent:

No odors and temperature/RH matched to the rest of the house, not any colder or more humid.

Why would a bathroom be stinky and/or humid when not in use?

 

[Denwood]

Denwood:

Nice info --- When I did my place in the city -- 4 story 1810 brick federal 4600sf I used a 80cfm unit and it was oversized. Whole placed spray foamed. I see people installing 300-400 cfm units is small houses.

How much dedicated venting are you required to do when no ducted systems?

If there is no forced air system to circulate fresh air from an HRV, a dedicated system of ducts must be added (normally 4-6” ducts) to service each bedroom, floors with no bedrooms, and common living areas where supply is kitchen and bathrooms. Zehnder makes some of the most efficient systems out there:

This video details their dedicated HRV piping system:

Adding a spot ERV like I did would satisfy fresh air requirements, but you’d need several as per the code above so not efficient or cost effective.

 

[yeldogt]

We don't have the same codes -- maybe because few homes are built without ducted AC in the USA. We do have the range make up air being enforced in a few areas.

We just don't build really tight buildings -- cheap energy has slowed the progress and upfront cost resistance.

I had a lot of problems with an early Zehnder unit (motor and bearing) media issues -- I hear they are much better today.

I'm an old house guy .. so, even with doing spray foam on all my projects I'm starting out with 19th century construction .. although you can get a fairly tight house.

Even with VS HVAC ...Whole house dehumidifiers are often needed in my area ... so I pipe an inlet from the outside ..... have set up for an ERV exhaust point but have not needed to install one.

 

[jgbnm]

The wife and I will hopefully be starting a build this spring to passive house standard. A ducted Zehnder Comfoair 200 is currently specced. A single Mitsubishi mini-split and two ducted zones for heating and cooling. Smallish house and big garage. I’ve visited a few similar homes and spoken to the owners who have been very happy with the results. Small dataset though...


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[yeldogt]

As we tighten up homes the need for ventilation increases -- doing so in a dry temperate climates w/o radon is easy.

The size of the unit depends on the size of the building and how tight ... all buildings leak.

The problem is the sizing -- too big and they waste energy w/o the homeowner knowing.

It's like many radiant slab systems -- the ability of a big boiler to overcome a bad install and leaking building allows installers to keep designing inefficient systems.

 

[Denwood]

The wife and I will hopefully be starting a build this spring to passive house standard. A ducted Zehnder Comfoair 200 is currently specced. A single Mitsubishi mini-split and two ducted zones for heating and cooling. Smallish house and big garage. I’ve visited a few similar homes and spoken to the owners who have been very happy with the results. Small dataset though...


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I would strongly encourage you to do a build thread! Are you going electric with everything with panels to offset?

Are you doing the ground loop preheat for the Zehnder HRV unit? It looks easy to do a brine loop if doing new construction. This brings temp delta for that unit to 1-2 F which is pretty amazing in cold weather. This pretty much guarantees that the HRV unit will never be in recirc mode to defrost.

 

[jgbnm]

I would strongly encourage you to do a build thread! Are you going electric with everything with panels to offset?

Are you doing the ground loop preheat for the Zehnder HRV unit? It looks easy to do a brine loop if doing new construction. This brings temp delta for that unit to 1-2 F which is pretty amazing in cold weather. This pretty much guarantees that the HRV unit will never be in recirc mode to defrost.

Yeah, I was thinking about it since things like the wall assembly, windows and air tightness are pretty unique. Interesting to me at least!

We have a full set of plans and should have a bid in Jan. If that’s close, we hope to start in the Spring. If not, may be delayed a bit. The lot has made the plan a big challenge due to buildable area and allowed elevations. About 1920 sq ft of heated space with about 1100 sq ft of garage.

Will be full electric with panels to offset. Energy modeling suggests around 3k watts needed I think - need to see the most recent number though. We have a buried line for moderating air intake temps in the plan.




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[yeldogt]

Yeah, I was thinking about it since things like the wall assembly, windows and air tightness are pretty unique. Interesting to me at least!

We have a full set of plans and should have a bid in Jan. If that’s close, we hope to start in the Spring. If not, may be delayed a bit. The lot has made the plan a big challenge due to buildable area and allowed elevations. About 1920 sq ft of heated space with about 1100 sq ft of garage.

Will be full electric with panels to offset. Energy modeling suggests around 3k watts needed I think - need to see the most recent number though. We have a buried line for moderating air intake temps in the plan.


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A build thread would be interesting ... I thought of doing one when I built my house along the Delaware river about 12 years ago ... The info and materials a challenge back then. I like the look of many... my better .. not so much.