I would not put in A HRV as they will pull out all of the moisture in the home Look at a high efficiency ERV (energy recovery ventilator) like the ER80M by UltimateAir it will will give you 100 CFM and 99% efficient so in the winter you won't cool your house down bringing fresh air in. also it is a merv12 filter. check out the website

ERV cores are more subject to frost damage in locations as cool as Wisconsin. HRVs are more robust, and as long as the ventilation rate isn't huge, it won't "...pull out all the moisture in the home...", by any means. Those CO2-emitting humans also emit H2O with every breath they take, and if moderating the ventilation rate to control CO2 levels only as-needed, the drying aspect will be minimal. Many choose to operate the HRV under dehumidistat control during the winter, which is usually more than enough to control CO2.

"99% efficient so in the winter you won't cool your house down bringing fresh air in"

Have not seen any specs this good. Sorry but I doubt it.

Posted By ChrisJ on 27 Apr 2017 04:58 PM
"99% efficient so in the winter you won't cool your house down bringing fresh air in"

Have not seen any specs this good. Sorry but I doubt it.

Third party test evidence is that it maxes out at 84% sensible recovery efficiency, but the include a "Apparent Sensible Effectiveness" column that hit's 99%. Whatever that means, it's not the same as 99% efficiency.: https://cdn2.hubspot.net/hubfs/92089/docs%20manuals/ER80M/Exova_testing_UltimateAir_ER80M_080116.pdf (Don't know anything about Exova Materials Testing Inc. who produced that document.)

So if Mr Energy gave you an accurate blower door test, your 3 ACH50 is not tight, even worse that it is a small house, 9000 cubic feet. Its not a tight house, at all. Weird that you get high co2 numbers, maybe you breathe too hard.

Or it is a tight house and something wasn't closed, or the blower door is way out of calibration, or they leave the frame loose to sell services, or it was windy, or they just didnt know what was going on. If it is correct, something isnt adding up, since 3ach isnt close to tight.

Could be the bedroom happens to be a tight room and the rest of the house has your significant leakage, you could figure that out with some zone pressure diagnostics, unfortunately they wont do that for free, probably cause they dont know what that is

Maybe it has to do with the fact we are in a shoulder season and air can go stale now unless you measured this across the heating season. Anyways you can use the cfm50 number and the 62.2 2013 formula to figure out your recommended ventilatilation requirement.

Greentree.. I was surprised I got 3 to 3.5 (depending on how you figure interior volume), although there were a number of small things I didn't have time to address before the test. But volume is taken into account when converting CFM50 to ACH50. I do wonder how much operator error enters into this....especially how tight they get the blower frame installed (I assume it matters). I may have to have it redone...by someone with experience. -mf

My comment regarding volume has to do with the fact that it is generally easier to airseal a smaller volume structure, less cracks holes and other situations to deal with.

For reader interest cfm50 # multiplied by 60 (minutes) divided by volume equals ach50, how many times the volume of your house will be completely replaced by outside air in one hour under 50 Pa of pressure.

If the blower door frame isnt tight in the opening it will fall into the house at 50Pa, an open window or door would be too obvious then it dawned on me how to cheat a blower door test, and i could be wrong because i havent attempted this yet, (i will try it) but you just have to set the wrong fan opening size on the gauge which would be very easy to do and virtually undetectable. You could swing a cfm50 number pretty hard by doing that.

Im not implying that is what was done, but that would be very easy to do.

You could do a basic supply only ventilation, good in the summer, not good in the winter, you could do an exhaust only, good in winter not so good in the summer except our a/c season is short so it maybe ok. Exhaust only replacement infiltration is random unless you added some sort of passive inlet or dampered intake. Cost/benefit of an hrv or erv is debatable. The whole deal is really dependant on your house, how you use it and what equipment you have, not something you can do over the internet. If you really are at 3 ach your house is a little more forgiving since its leaky.

Note that a house that measures 3 ACH50 will have 0 ACH0. So without forced ventilation, you will often have an air quality problem.

Another big factor here should be # of occupants and pets (at least as far as CO2 and O2 levels go). I suppose a house should be designed around # of bedrooms etc, but that doesn't dictate how many people will end up living there. A habitat house not far away seems to have at least 6 people in it, for ex. And what do people in Tiny houses do? I doubt id they spend moola on HRV's. I designed this house for just one (me). If my "family" grows, then I might be forced into an HRV.

I'd also like to know more about what health effects CO2 are. Or is it mostly just an indicator of tightness (and therefore toxin buildup)? I'd be more worried about low O2 levels, but not sure if there's a perfect inverse relationship between CO2 and O2. Maybe I could just monitor my blood O2 during the night with a blood oximeter and see if it's dropping. But if it does, it could be from apnea..

thanks,
-m

Jon,
Love to hear more about your theory of no natural pressure in buildings. Maybe expound in a little more detail on no natural pressure differentials due to temperature, wind, fans, farts, opening a door, ect in the world you live in.

Pbrane, CCHRC , google that, has done air quality white papers on small houses in alaska i believe, you might want to read up. What I find is the ventilation standard is a catch all and therefore inefficienct as every situation is different, the equipment isnt there to cost effectively and easily make air quality assessments when you comission a house.

You could have errors in your co2 detector, especially if its a cheap model and are a hypocondriac like my brother, point is put the hrv in or buy some plants since it sounds like your mind is already made up.

In the old times people would crack a window when the house got stuffy, that could arguabley be the "greenest".

Posted By greentree on 01 May 2017 03:43 AM
Jon,
Love to hear more about your theory of no natural pressure in buildings. Maybe expound in a little more detail on no natural pressure differentials due to temperature, wind, fans, farts, opening a door, ect in the world you live in.

Those differentials aren't zero are they? (By definition!) But they're also not sufficient for hitting ASHRAE 62.2 ventilation levels (or any reasonable fraction thereof), at least in most houses, most of the time, and the intake & exhaust paths may not be locate where needed the most.

most, most, may. That's why we need testing.

Every house is different, every house is USED differently, every house leaks from different spots due to various things that happened when it was built. Some general assumptions can be made, yes, but you don't know jack until you test it.

BTW, I got a new blower door today so I tested my house and switched the fan settings on the gauge to see how skewed the results got. My house setup correctly with corrections in tectite is 361 CFM50 or .53 ACH50. If I switch the digital gauge to tell it it's on a bigger ring when it really isn't I get 1113 CFM50, 1.65 ACH50 on ring A and 2968 CFM50 4.4 ACH50 on open fan, all the while its really chugging along at 361 CFM50 on ring B. If I wanted to try to impress you I could take a picture of the gauge set on Ring C which would show 136 CFM50 and .20 ACH50. Trust your blower door operator.

greentree.. That's a pretty tight house you have. Congratulations. That calculates to an interior volume of 40,868 ft3, if I figured right. How do you calculate interior volume? I understand there are a few different methods. I've seen some experts question the cost effectiveness of getting a house that tight....especially a large house. I'd love to know your cost/ft2 to build, unless it's too personal...that's cool. Thanks, -m

My cost per square foot isnt going to mean much, im a builder and when a builder builds his own house you get all kinds of favors you dont normally get. Mound system for $8800?, thats crazy days pricing. It's about 2800 sf finished, the whole 4600 is conditioned. Market rate on that would be around $130-140 ft finished, im significantly under that. I calculate volume to the exterior on my new homes because that is what i consider my air barrier and primary pressure plane to be.

I think I went through maybe 6 cases of sealant and 2 cases of 1 part, Im not into the tapes. Framing cost extra is negligible, my time, maybe 30-40 hours to air seal. I do it myself, a few key times during framing, before and after trades and one last check before we staple the insulation netting up.

Ive been doing the same things for years and the results are always great and from the ones ive tested down the road the seal has lasted, hopefully they arent rotting.

Pbrane,

You inspired me so I ordered a co2 detector and started reading about it. Apperently global avg background co2 is 385 ppm so you test outside first then test inside and do the simple math above background co2 to get your value, apparently you can estimate your ventilation rate based on that figure. Pretty interesting stuff. ill do some data logging with some different scenarios and let you know what I get. I did our bedroom closed door and averaged 1048 ppm.

Mine also goes up to between 1000 to 1200 ppm in the bedroom if I close the door. I've noticed some weird readings. I wish I had one in every room, so I could see where the highest concentrations are etc. I could move it around, I suppose. Anyway, I've noticed some readings that don't make sense. for my meter, to "calibrate" it, you take it outside for 30 minutes and let it reset to 400 ppm. Then inside, the lowest I've had (house closed up) was around 600. Here's mine: https://www.co2meter.com/products/tim10-desktop-co2-temp-humidity-monitor

Note that there are good reasons to ventilate that have little relation to CO2 level.

Jon, like what? Usually a response should contain some useful information rather than a cryptic proclamation.

I think what you're trying to allude to is: don't measure co2 levels in a home and assume you have wonderful air if the ppm is low. I totally agree with that whether that is what you meant or not, its not a pass/fail.

But, it appears co2 measurements are very useful.

Following is a quote from a study that reports on the negative effects of high co2 concentrations that sums up all the professional articles and studies Ive looked at so far that sums up what is an obvious common theme:

"It has been widely believed that these associations exist only because the higher indoor CO2 concentrations occur at lower outdoor air ventilation rates and are, therefore, correlated with higher levels of other indoor-generated pollutants that directly cause the adverse effects,” such as volatile organic compounds and particulates." -study from Harvard School of Public Health. Reported on thinkprogress.org.

What is obvious is professionals agree that co2 readings indicate the quality of mixing with outdoor air.

> don't measure co2 levels in a home and assume you have wonderful air if the ppm is low

Correct, that was the point. For example, a large volume of interior space to occupant ratio and a low outdoor ACH ventilation rate will show a low CO2 level. But non-occupant related pollutants (eg, various VOCs) are likely to be high.

Correlation is far from accurate measurement. But a CO2 sensor reading, under steady state conditions and adjusted for interior volume, base CO2 level, current number of occupants and activity level, could be used as a tracer gas to estimate the current ACH-natural. But lacking that - use forced ventilation at ASHRAE 62.2 rates. And even that involves the assumption that there isn't anything releasing more than expected amounts of indoor pollution.

A google search for "indoor air quality ventilation" will elaborate far more than I ever could.