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Old 02-01-2010, 06:49 PM   #1
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HRV retrofit as a result of energy audit


Hi all,

I have a situation where I've sealed my 40 year old bungalow to where a door blower test has my ACH natural down to 0.154. I'm told that as a result of this I should really invest in an HRV, I understand that an HRV retrofit isn't optimal but I feel like I should be doing the best I can to get fresh air in over the fall/winter. (Living in eastern Ontario, near Ottawa).

Due to a number of construction issues I'm absolutely limited to the follow when it comes to installation:

Must use a tandem transition kit for both intake and exhaust.
I have an older (12 year old) furnace, so no dc motor, therefore I can't install it as fully ducted or simplified, as I cannot run the blower continuously. Also, I don't want my blower tied to the HRV, I'm reading that this creates a drafty feeling in the house.

The best I can tell is that I'm limited to installing the HRV using the Central Draw point method.

I have a Venmar HEPA 3100 in mind and I'm considering installing it myself but I have a few questions:

The central draw point method documentation states that the stale supply
should come from a register at the highest point in the house. In my house I only have floor supplies. Would I need to create a return from the ceiling level on my main floor? If so what size return does it need to be? Is there a maximum length? Can it be rectangular ducting in the wall cavity? What solutions do you have?

Lastly, in the installation guide for the product there's no mention of balancing the airflow. If I install the unit myself how do I get it balanced? Will HVAC specialists come out and balance it for me?

Thanks so much!

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Old 02-01-2010, 09:37 PM   #2
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HRV retrofit as a result of energy audit


If you pay them enough they will.

How much air in CFM do you need to get your ACH to .2 or .25?

Do you have an attic?

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Old 02-01-2010, 10:19 PM   #3
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HRV retrofit as a result of energy audit


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Originally Posted by beenthere View Post
If you pay them enough they will.

How much air in CFM do you need to get your ACH to .2 or .25?

Do you have an attic?
Yes, I have an attic but up here in the great white north it's below 0c all winter long, from the documentation I've seen HRV's cannot operate below 0c.

As for the CFM required to achieve ACH of .2/.25 I'm not sure. I'll try to find out. Why do you ask? For sizing purposes perhaps?

Thanks
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Old 02-01-2010, 11:19 PM   #4
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HRV retrofit as a result of energy audit


They can operate below 0C. If they can't. Then no use having one in the winter.
You may be thinking of ERV's which need frost protection under 0C.

I have some installed in attics.

But. What i was wondering. do you have a closet that you can run the stale air intake up to the attic, and draw from the Ceiling then.

Yes, I asked for sizing.
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Old 02-03-2010, 08:53 PM   #5
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HRV retrofit as a result of energy audit


Quote:
Originally Posted by beenthere View Post
If you pay them enough they will.

How much air in CFM do you need to get your ACH to .2 or .25?

Do you have an attic?

The auditor was able to tell me that the computer program comes up with 30cfm continuous, and isn't sure how that translates into HRV sizing.

According to her calculations on my home is 15795 cubic feet.

Thanks
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Old 02-03-2010, 11:38 PM   #6
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HRV retrofit as a result of energy audit


You should have gotten a report that says how much air your house is currently leaking(ACH).

Was this a foot in the door BD test. Doesn't sound like they did much to evaluate your home.

To bring a house your size up from .154 ACH to .2 by what you posted would only require 12CFM continuous.

30CFM continuous is 1800 cubic foot an hour.

To have 1 air change an hour. You house needs to have an hourly exchange rate of 3,159 cubic foot an hour. Or 53CFM.

So if that 30 CFM they came up with is the additional you need.

You only need a small HRV/ERV.

Most will be able to give you he required air in less then 20 minutes of run time. That 3100 has a 70 CFM rating at low speed, and 105 at high speed.

I would suggest that you install the stale air intake in the ceiling in a central location.
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Old 02-04-2010, 10:01 PM   #7
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HRV retrofit as a result of energy audit


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Originally Posted by beenthere View Post
Most will be able to give you he required air in less then 20 minutes of run time. That 3100 has a 70 CFM rating at low speed, and 105 at high speed.
Okay, the above sounds good. I'll try to get more information out of the auditor. The report isn't complete yet as I'm waiting to add the HRV to the energy retrofit so I can get the rebate for it.

With respect to the 3100, is there any way I could have it balanced down enough to use it? I ended up getting a great deal on it and it has the hepa filter that I like.

Thanks
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Old 02-04-2010, 10:05 PM   #8
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HRV retrofit as a result of energy audit


Run it off a timer.

Set the timer for what ever number of minutes an hour you need. Many HRV'ERVs have their own timers for this.

Some thermostats incorporate a ventilation timer in them.

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