Ventilation Systems

[My Dream]

As part of the eco energy audit in Canada, I was told that I would benefit by installing an energy recovery ventilator. I somewhat understand the principal and got this explanation below:

Energy Recovery Ventilation (ERV) is the process of exchanging the energy contained in normally exhausted building or space air and using it to treat the incoming outdoor ventilation air in residential and commercial HVAC systems. The benefit of using energy recovery is the ability to meet the ASHRAE ventilation & energy standards, while improving indoor air quality, and reducing total HVAC equipment capacity.

An Energy Recovery Ventilator (ERV) is a type of air-to-air heat exchanger that not only can transfer sensible heat but also latent heat. Since both temperature and moisture is transferred, ERVs can be considered total enthalpic devices. On the other hand, a Heat Recovery Ventilator (HRV) is limited to only transferring sensible heat. HRVs can be considered sensible only devices because they only exchange sensible heat.



The eco energy rebates allow for $750.00 for the above unit but is it really worth it. I still need to price one out and don't know if I can do the install myself even though I'm fairly mechanically inclined. This week we’re having a high efficiency furnace and a/c unit installed but I don’t know if that adds to the ERV.

[kumquat]

Unless your house is very well sealed (e.g. built to R2000 standards) is probably leaks enough air that any air-to-air heat exchanger is not very efficient since the bulk of the air exchanged bypasses the system.

This, BTW, is the opinion of someone who really doesn't have a clue.

[Bimmerbill]

Sounds like a heat-pump?

[ls99]

AKA air to air heat exchanger. Most residential structures leak a lot. I you really want to know how airtight is your house, get a blower door test. They remove a door, install atemporary barrier with a fan in it, then pressurize the house. With instruments they can measure the leakage rate. The folks doing the testing can tell you if the house is well sealed or leaks like a sieve. Got to measure to know. Numbers is good.

I would not spend any money on the ERV.

[My Dream]

I had an eco energy audit done about 2 weeks ago but haven't received a report back for the government yet. He did say that I had a lot of leaks but told me how to close most of them. He also used the blower test to determine where the leaks were but I think he's done the leak test so many times that he already knew where the would be before he turned on the machine.

After the leaks have been sealed for the most part, is it still work the energy savings to have a ERV what with the rebates the gvmt. is giving. ?

[ls99]

Highly unlikely that you can make it so airtight that a ERV will be needed. Call me a a realist.

Edit add: A good clue to an airtight house, the humidity level in the wintertime keeps going up, exceeding 60% and then some. If it hovers around 20 to 30% you still have plenty of uncontrolled airflow through the structure.

[My Dream]

Right now the relative humidity in the house is at 48% with the humidifier going so I'll turn it down and see if it maintains that amount. Thanks for the tip.

The only reason I'm considering it is due to the eco rebated of $750.00. A Venmar 2600 is about $750.00 and the installation kit is around $130.00 and I figure I could do my own install, therefore the unit would end up costing me around $200.00

[samclem]

Quote:

Originally Posted by My Dream .The only reason I'm considering it is due to the eco rebated of $750.00. A Venmar 2600 is about $750.00 and the installation kit is around $130.00 and I figure I could do my own install, therefore the unit would end up costing me around $200.00

The unit will also cost money (and energy) to run. There's a fan in it, and that uses unergy. In addition, it will not be 100% effective in recovering all the heat from the air it sends out of your building envelope and transferring it to the incoming air.

You need one of these devices if you have a problem with the indoor air quality in your home. It will not save you energy, it will cost energy. It is a good solution if your home is very tight and therefore the indoor air is of poor quality (high humidity, not enough air exchange to get rid of offgasing and cooking odors, etc).

[My Dream]

If that's the case samclem then it makes me wonder why the government is offering home owner $750.00 in eco energy rebates if they install one in there home? If it's not very energy efficient then why so much of a government incentive to get one.

I'm not quite understanding the concept.

[travelover]

Quote:

Originally Posted by My Dream If that's the case samclem then it makes me wonder why the government is offering home owner $750.00 in eco energy rebates if they install one in there home? If it's not very energy efficient then why so much of a government incentive to get one. I'm not quite understanding the concept.

I got an energy rebate for installing a skylight even though I'm sure it leaks more heat energy than it saves in lighting energy. Samclem is right, unless your house is really, really tight, it will just waste energy.

But if you really want one, buy it. Maybe in the future you'll tighten up the house to the point where you'll need it.

[My Dream]

Quote:

Originally Posted by travelover I got an energy rebate for installing a skylight even though I'm sure it leaks more heat energy than it saves in lighting energy. Samclem is right, unless your house is really, really tight, it will just waste energy.

In Ontario we get a $80 rebate for replacing an existing skylight to an energy efficient one based on rough opening but not for installing one that didn't previously exist. I guess your area is different.

As for air tight, I'm in the process of sealing up as many air leaks as possible but I doubt I'll do more once the audit is over so it's now or never. I'm still not sure why the $750. rebate if the results are that efficient.

Thanks everyone.

[samclem]

Quote:

Originally Posted by My Dream If that's the case samclem then it makes me wonder why the government is offering home owner $750.00 in eco energy rebates if they install one in there home? If it's not very energy efficient then why so much of a government incentive to get one. I'm not quite understanding the concept.

Well, it's always dangerous to apply logic as a means of understanding government programs.

It is possible (though difficult with an older home) to tighten up the air envelope to such a great extent that the home develops indoor air quality problems. The government functionaries that devised the program probably envisioned that these situations might occur, so they allowed credits for the ERV. In your situation, with a nearly 100% rebate, I might be tempted to get one, if you can install it yourself without much trouble. You don't have to actually run it. As travelover says, maybe later you will get the house even tighter and you'll want to run it.

As an aside, I thought the approach offered by this SmartVent home ventilation system is interesting. It is different from an ERV as it does not heat up/cool off the incoming outside air using the heat from the air that is being sent out. Instead, I think it has sensors for indoor temp and humidity and outdoor temp and humidity, and just pumps (filtered) outdoor air into the home when it is needed inside AND when the outdoor air is "right" (i.e. when it's introduction will serve to make the indoor air humidity closer to optimum). Cheap, and it results in a slight positive pressure in the building envelope, when it is running, which is generally good. But, I don't need one.

[My Dream]

l read that it's aways good to have air moving within a house, which is why I even considered the ERV.....that along with the rebate of course. The furnace may not always accomplish this depending on the season. I still haven't decided whether to purchase the Venmar 2600 which is $739.00 + $129.00 for the installation kit. Again I would only purchase it if I were to install it myself and am confident that I would see any benifit. The item you've posted samclem won't qualify for the rebate therefore it wouldn't consider it.
I'm in no hurry since we still have over a year to decide. We just got our new furnace and a/c installed last week, windows go in beggining of Decemeber so I've got more reading to do on the benifits of ERV's.