From an energy-conservation point of view, introducing fresh air into a house is a waste. You will have to get rid of existing heated air, in order to introduce fresh air, so introducing fresh air will be an energy loss, and therefore, a financial loss.
Quote:
Originally Posted by Drake
I'm just not yet sure of an HRV real savings as its theory.
|
The energy saved by an HRV, even an extremely efficient one will be very small. The direct pay-back will be long... you might not live long enough to see an HRV that you install, ever break even.
Whether or not you bother to put one in depends on whether the entire house has reduced infiltration to extremely low levels... If you live in an air-tight house, it will feel uncomfortable from the beginning, and eventually it will affect your health.
Even if you choose eco materials in your house, you still bring in toxic materials. For instance, new clothes are treated with toxic substances which out-gas, new furniture with synthetic fabrics and foam cushions contain toxic materials which out-gas, any plastic that flexes contains toxic materials which out-gas, cleaning products contain toxic materials, carpet and carpet padding is loaded with toxic materials which out-gas, as are many beds and bedding which out-gas, sheetrock is covered on both sides with pre-processed cellulose (AKA: paper) which easily supports mold growth which enters indoor air... I personally know people whose immune systems
have essentially collapsed under the sustained load of environmental toxins, and they now have to live in extreme conditions to avoid further exposure.
This is why we want adequate ventilation, to avoid the buildup of toxins (and oxygen depletion/CO2 buildup) in our air... It is a compromise we make in order to continue a healthy life.
If you live in a house that has enough leaks to flush out the mold (which is everywhere) and CO2 and toxins from your air, you would be a fool to spend $2000 on an extremely high efficiency HRV to recover a few dollars worth of heat every month. In fact, the power to run an HRV might cost you more than the recovery value of the energy saved.
Fortunately for you, this is something that you can measure... you don't need to take the advice of strangers who may not actually know what they are talking about. Hire a certified blower-door operator to come in and do a blower door test to actually determine what your infiltration rate truly is. The companies that do this are already quite familiar with what constitutes the level of critical tightness, and they can advise you if you need mechanical ventilation... they probably already know which brands of HRVs actually work the best, I am hearing the same brand names from several independent groups and agencies... you don't have to guess on this.
But if your house is critically tight, it would be false economy not to mechanically ventilate. Health is more precious than a few paltry dollars.
Quote:
Originally Posted by Drake
Oxygen/CO2 are a concern but what level of ACH will cover just that?
|
The German Passive House Initiative tested this very thing, because they had achieved air-tight house construction, and people were uncomfortable and people were getting sick. The minimum level they came up with is 0.35 ACH.
They also determined that at the critical levels of tightness, natural infiltration alone was not adequate to supply continuous fresh air... on windy days it was fine, but over several consecutive days of relatively still air, natural infiltration was insufficient.
* * *
It all depends on the level of natural infiltration in your house, which you should measure.
You don't need to risk getting bad advice and you don't need to guess about this one.
-AC