HRV Sizing

[Klientool]

Hello
I am having some issue with my HRV freezing up after a little research came up stating the unit is not balanced upon further research I found some information around sizing. In Edmonton Alberta the sizing of the unit for 2330 Sq Ft home newly built with basement undeveloped therefore a total of 3352 Sq Ft equated to 70L/S or 148 CFM. So the contractor installed a Lifebreath that says it can do 152CFM model RNC6-ES on High Speed. When the unit is balanced it is operating at approx 85 Fresh to 75 Stale using a manometer and door ports for balancing at highest speed. After further research the Building Code stipulates that you must have 0.35 ach this unit does not do that at balanced 85 CFM of fresh air on high speed.

I am wondering if I am misunderstanding the code requirements does the unit have to be able to do 148 CFM on High once balanced and installed?

Or is the unit only to be designed to 148 CFM and once installed and balanced that number does not matter?

The building contractor has no clue he did not even know how to balance the unit he came once and pretended to balance it but changed no baffles on the top of the unit spent over 2 hrs in the furnace room trying to get it to balance. So I bought my own mano meter and did it myself.

Thanks

[teddy bear]

Keep in mind that the balanced flow adds to the natural infiltration/exfiltration and exhaust air from clothes drier and the kitchen hood. Over ventilation during cold, weather is more common. During calm winds and mild temperature is when you need the max capacity of the HRV. Monitoring the CO2 levels verses the number of occupants, when occupied will give the true air change rate. Also the amount of moisture in the air in the home verses the number of occupants and moisture in the outside air.

2,330 sq.ft. X 9 ft. ceilings= 20,970 FT^3

20,970 / 85 cfm = 246 minutes (4 hours) plus natural infiltration and mechanical exhaust.

This home will be too damp during high outdoor dew points and too dry during cold weather low outdoor dew points except during high occupancy.

If you want more, enlarge the ducts on the HRV.
Your thoughts?

Regards Teddy Bear

[Klientool]

Keep in mind that the balanced flow adds to the natural infiltration/exfiltration and exhaust air from clothes drier and the kitchen hood. Over ventilation during cold, weather is more common. During calm winds and mild temperature is when you need the max capacity of the HRV. Monitoring the CO2 levels verses the number of occupants, when occupied will give the true air change rate. Also the amount of moisture in the air in the home verses the number of occupants and moisture in the outside air.

2,330 sq.ft. X 9 ft. ceilings= 20,970 FT^3

20,970 / 85 cfm = 246 minutes (4 hours) plus natural infiltration and mechanical exhaust.

This home will be too damp during high outdoor dew points and too dry during cold weather low outdoor dew points except during high occupancy.

If you want more, enlarge the ducts on the HRV.
Your thoughts?

Regards Teddy Bear

Thanks for the reply

Also I am having the basement finished and in Canada the sizing is calculated via amount of rooms which equates to 148CFM required.

I am not sure I understand what you are telling me with your cubic ft statement 20970/85 = 246 mins? In Canada the basement would be included in the calculation so it would calculate to 29146/85 = 343 mins? This would be at full speed also which would only be on when using washrooms or showers otherwise it would run a speed 1.

Enlarging the duct size would be very difficult considering the house is finished and the stale air vents are through out the house in the bathrooms. Can one not purchase a larger CFM unit?
The home is build to the 2019 building code here which I would say is very tight construction. I do not foresee much infiltration from Triple Pane windows R50 in attic and R21 in walls including basement. Other than when the vent for dryer and oven are on.
According to the loadcalc.net it requires 135 CFM so this where things become very confusing what is the proper size? and is it to be sized to handle that much CFM when running?

Thanks again

[Restaurant Mech]

My understanding is that code means it must do that cfm minimum.
Now, once code is satisfied it's time to actually make things work properly.
The best way is to measure co2 levels in the house, and set the hrv to run and maintain lower co2 levels when occupied.
Now my experience has been to run a unit like on low speed basically whenever the house is occupied. It's not a perfect or totally efficient way, but it's reliable.
I've found that even 80 cfm of fresh air continously circulating to work pretty well at keeping oxygen levels high inside the house with up to 4 people.
But remember, every house is different. And that's what code doesn't recognize.

[BALloyd]

2018 building code in Canada requires ventilation of the structure 24/7/365. Different ways of doing it but HRV is a popular choice. Usually set to run at low speed constantly and ramp on a demand such as a humidity.

My understanding is that code means it must do that cfm minimum.
Now, once code is satisfied it's time to actually make things work properly.
The best way is to measure co2 levels in the house, and set the hrv to run and maintain lower co2 levels when occupied.
Now my experience has been to run a unit like on low speed basically whenever the house is occupied. It's not a perfect or totally efficient way, but it's reliable.
I've found that even 80 cfm of fresh air continously circulating to work pretty well at keeping oxygen levels high inside the house with up to 4 people.
But remember, every house is different. And that's what code doesn't recognize.

Sent from my SM-G965W using Tapatalk

[BALloyd]

Hello
I am having some issue with my HRV freezing up after a little research came up stating the unit is not balanced upon further research I found some information around sizing. In Edmonton Alberta the sizing of the unit for 2330 Sq Ft home newly built with basement undeveloped therefore a total of 3352 Sq Ft equated to 70L/S or 148 CFM. So the contractor installed a Lifebreath that says it can do 152CFM model RNC6-ES on High Speed. When the unit is balanced it is operating at approx 85 Fresh to 75 Stale using a manometer and door ports for balancing at highest speed. After further research the Building Code stipulates that you must have 0.35 ach this unit does not do that at balanced 85 CFM of fresh air on high speed.

I am wondering if I am misunderstanding the code requirements does the unit have to be able to do 148 CFM on High once balanced and installed?

Or is the unit only to be designed to 148 CFM and once installed and balanced that number does not matter?

The building contractor has no clue he did not even know how to balance the unit he came once and pretended to balance it but changed no baffles on the top of the unit spent over 2 hrs in the furnace room trying to get it to balance. So I bought my own mano meter and did it myself.

Thanks

Is your unit exhausting your bathrooms as well or do they have their own exhaust fans?

Is there a humidity controller?

Did you see the ductwork for the HRV or can you still see any of it? Is it flexible ductwork or hard metal?

New construction low bids are notorious for installing the ductwork incorrectly, which chokes off your air flow.

Sent from my SM-G965W using Tapatalk

[teddy bear]

Thanks for the reply

Also I am having the basement finished and in Canada the sizing is calculated via amount of rooms which equates to 148CFM required.

I am not sure I understand what you are telling me with your cubic ft statement 20970/85 = 246 mins?

This is the cubic feet of volume in current living area divided by the current fresh air flow equals the minutes for an air change. Also keep in mind that a 20 mph wind has the same effect as 50 Pascal blower door test.

In Canada the basement would be included in the calculation so it would calculate to 29146/85 = 343 mins? This would be at full speed also which would only be on when using washrooms or showers otherwise it would run a speed 1.

Enlarging the duct size would be very difficult considering the house is finished and the stale air vents are through out the house in the bathrooms. Can one not purchase a larger CFM unit?


The home is build to the 2019 building code here which I would say is very tight construction. I do not foresee much infiltration from Triple Pane windows R50 in attic and R21 in walls including basement. Other than when the vent for dryer and oven are on.
According to the loadcalc.net it requires 135 CFM so this where things become very confusing what is the proper size? and is it to be sized to handle that much CFM when running?

Thanks again

I would suggest adding ducts to the current unit to the basement remodel for the needed air flow.

Regards Teddy Bear

[dan sw fl]

Thanks for the reply

Also I am having the basement finished and in Canada
the sizing is calculated via amount of rooms which equates to 148 CFM required.

I am not sure I understand what you are telling me with your cubic ft statement 20970/85 = 246 mins?

In Canada the basement would be included in the calculation so it would calculate to 29146/85 = 343 mins?

Enlarging the duct size would be very difficult considering
the house is finished and the stale air vents are throughout the house in the bathrooms.

Can one not purchase a larger CFM unit?

The home is build to the
2019 building code here
which I would say is very tight construction.

I do not foresee much infiltration
from Triple Pane windows R50 in attic and R21 in walls including basement.

Other than when the vent for dryer and oven are on.

According to the loadcalc.net it requires 135 CFM
so this where things become very confusing what is the proper size?

And is it to be sized to handle that much CFM when running?

Thanks again

I would operate a _ HRV at 105 CFM _ for 18 hours /day.
0.3 ACH for 2,330 sq feet floor area at 9' wall height

Monitor CO2 and adjust HRV accordingly.



ATTACHMENTS

[dan sw fl]

Hello
I am having some issue with my HRV freezing up after a little research came up stating the unit is not balanced upon further research I found some information around sizing.
In Edmonton Alberta,
the sizing of the unit for 2330 Sq Ft home newly built with basement undeveloped
therefore, a total of 3352 Sq Ft equated to 70L/S or 148 CFM.

So the contractor installed a
Lifebreath that says it can do 152 CFM { @ 0.4" }
model RNC6-ES on High Speed.

When the unit is balanced it is operating at approx 85 Fresh to 75 Stale
using a manometer and door ports for balancing at highest speed.

After further research the Building Code stipulates that
you must have 0.35 ACH.
This unit { BASED on Quite Poorly installed duct work }
does not do that at balanced 85 CFM of fresh air on high speed.

Thanks

https://www.lifebreath.com/us/produc...entilator-hrv/

ATTACHMENT

[Klientool]

Is your unit exhausting your bathrooms as well or do they have their own exhaust fans?

Is there a humidity controller?

Did you see the ductwork for the HRV or can you still see any of it? Is it flexible ductwork or hard metal?

New construction low bids are notorious for installing the ductwork incorrectly, which chokes off your air flow.

Sent from my SM-G965W using Tapatalk

There are 3 bathrooms which do not have exhaust fans and the masterbath which does have an exhaust fan along with the HRV Duct

Yes the humidity is controlled.

The duct work to the stale air vents out of the HRV in the basement are hard metal. The air intake and air exhaust are insulated flex and the fresh to furnace is flex.

[dan sw fl]

There are 3 bathrooms which do not have exhaust fans and the masterbath which does have an exhaust fan along with the HRV Duct

Yes the humidity is controlled.

The duct work to the stale air vent[s] out of the HRV in the basement are hard metal.

The air intake and air exhaust are insulated flex and the fresh to furnace is flex.

Use (improper installation) of Flexible Duct is frequently the problem.

Replace with METAL duct.

[Klientool]

Right and the W.G. I get it balanced to is around 1.02 on fresh that's with the fresh to furnace dialed down to balance out to exhaust. The contractor is suspect for knowledge in this area. When I asked what this HRV was for his comments was to make utility bill cheaper not to bring in/out fresh air due to eff. in air tight homes