HVAC Techs - I need and ERV/HRV

[donnyj08]

I need some help on deciding on an HRV or and ERV for my new home built in Zone 4 North central Kentucky. I’m a weatherization contractor by trade and I’ve air sealed every single step of the way through my complete build. I however have limited knowledge on HRV/ERVs as I rarely ever find an existing structure that I can get this tight.

I ran a blower door test on my home I’ve been building and I’ve blown 335cfm @ 50Pa on a 2500 sf home. 23,800sf of volume. This gives me and ACH (air change per hour) of 0.83ACH50 if my math is right, and the crawl space is not encapsulated yet so I expect to shave another 35-50CFM on those numbers minimum.

with a house this tight what type of mechanical ventilation system do you recommend? I didn’t expect to get much tighter than 1.5ACH50 so I did not plan to buy a ventilation system, but now I definitely need one to exchange fresh air and remove stale air from the home.

 

[97K15004WD]

What's the code requirement for humidity control, if any, in your area?

What your goal with this project? Saving money, IAQ, etc.

 

[donnyj08]

What's the code requirement for humidity control, if any, in your area?

What your goal with this project? Saving money, IAQ, etc.

There isn’t a code for humidity Control in my area. The goal is comfort with adequate breathing air for humans in the home. The structure will remain as air tight as possible keeping the home as efficient as possible. As far as budget for ventilation I don’t have a set price. Most erv/HRV units run about $1k plus installation and setup so in the $2-3k range is probably average installed and I’m okay with that. I just want recommendations.

 

[donnyj08]

There isn’t a code for humidity Control in my area. The goal is comfort with adequate breathing air for humans in the home. The structure will remain as air tight as possible keeping the home as efficient as possible. As far as budget for ventilation I don’t have a set price. Most erv/HRV units run about $1k plus installation and setup so in the $2-3k range is probably average installed and I’m okay with that. I just want recommendations if there are any HVAC professionals on the site that may have insight. I’m planning to contact a few local HVAC companies this coming week.

 

[mightymousetech]

ERV is ALWAYS better than HRV.

Upgraded our condo supplied HRV for an ERV.

 

[sloinker]

I know zero about this subject but I did stay at a Holiday Inn recently. I was wondering if you could install a powered louvered vent in the attic space that is adjustable from your living area along with a powered/mated louvered intake as far from the exhaust as possible in the main living space. Maybe with an evacuation fan to drain heat build up in the summer. Just my thoughts.

 

[donnyj08]

ERV is ALWAYS better than HRV.

Upgraded our condo supplied HRV for an ERV.

I appreciate the input. I don’t necessarily need the heat portion from the HRV anyway as I have plenty of capacity on the HVAC system.

I will do some research on ERVs for my climate and talk with the hvac companies about it

 

[EA82]

In Florida we have used dehumidifiers a few times to basically draw outside air dehumidify it and introduce the dry air back in the return duct in some higher end houses. I'm sure this doesn't apply in colder less humid climates.
More often all that is required by code is just fresh/make up air coming straight to the return duct with an electronic damper.
From what I've read the difference between your 2 options is their ability to control humidity, consult with a local hvac expert as for what works best for your climate.

 

[tshephard]

I'm a big fan of real world testing.
Why not build the house/system, leave a space (clear wall port area, section of plenum, etc) and see if oxygen goes down?
Perhaps your personal patterns are such that door operation/minor leaks cover your needs.

 

[bullwinkle]

I do refrigeration, not HVAC, but you'll need some way to introduce outside air into the system (usually a basement outside air supply connected to the air return) & exhaust it with ridge/soffit vents in the roof/attic. Otherwise you're going to have moisture buildup in areas you don't want it-like in your insulation or underside of the roof.

 

[BMWTurboDzl]

Remember a ERV is an HRV that also provides some moisture transfer. Ultimately it depends on the number of occupants and any other indoor sources of moisture. This blog may help.

Why You Probably Need an ERV, Not an HRV - Energy Vanguard

The simple answer to the common question of ERV versus HRV is that you probably need an ERV. Here's why you want moisture recovery, too.

www.energyvanguard.com

 

[Fitter30]

HRV transfers heat while an ERV transfers both heat and moisture. Since Cincinnati has high humidity in summer hrv would be a better choice.

 

[BMWTurboDzl]

HRV transfers heat while an ERV transfers both heat and moisture. Since Cincinnati has high humidity in summer hrv would be a better choice.

You would think but remember cold air is dry air so with a HRV cold dry air exiting the house will not transfer any incoming moisture whereas an ERV will transfer some moisture like both transfer some heat. Some but not a lot. The issue with both is the shoulder seasons. AC isn't running but you still need to remove humidity so one might need a whole house dehumidifier. Ugh..so complicated.

 

[BMWTurboDzl]

ERV is ALWAYS better than HRV.

Upgraded our condo supplied HRV for an ERV.

Building codes in the US are behind Canada in this regard. Energy is cheap (inexpensive or can be offset with solar) which acts as a disincentive to building tighter homes.

 

[Fitter30]

HRV transfers heat while an ERV transfers both heat and moisture. Since Cincinnati has high humidity in summer hrv would be a better choice.

The thing i would want to do is add humidity in the summer, heating season a humidifier would be needed regardless.