Will Balanced Ventilation Be Required by Code?

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"You know where this is going, right? Codes will eventually require balanced ventilation." I've heard people say this more than once in the past year or so. As someone who has been attending the semiannual meeting of the ASHRAE 62.2 committee, I've been skeptical. Then I read the new Aspen energy code and saw the first evidence that this really could happen.

Yes, I held out on you yesterday. I published that article about Aspen's Simplified Equivalent Compliance Alternative, but I didn't tell you about any of the other provisions in their new code. Here's another one that, as far as I know, isn't required anywhere else yet.

Section R403.6.2 Balanced ventilation. (added section)
Dwelling units shall be provided with a mechanical balanced ventilation system. Heat or energy recovery ventilation systems shall have a minimum sensible heat recovery efficiency of 65% determined in accordance with CSA 439 at 0° C and at an airflow greater than or equal to the system's design whole-house mechanical ventilation airflow.

And of course they added the meaning of "balanced ventilation" to the list of definitions:

BALANCED VENTILATION SYSTEM. A mechanical ventilation system providing simultaneous outdoor airflow and exhaust airflow within 20% of each other.

Aspen is a cold climate. That means the skiing isn't nearly as good in the summer. It also means nobody with any experience in the area would use a supply-only ventilation system. That's for hot and mixed humid climates. But there's plenty of exhaust-only ventilation systems. The problem is they suck.

Balanced ventilation is definitely the way to go. The problem is it's more expensive. Especially if you're going to require that it be done with some kind of heat recovery, which is what Aspen is doing.

I imagine no one will be able to afford the houses there anymore and the place is just going to become another piece of American carnage, victim of a bunch of city bureaucrats that overreached with economy-strangling regulations. At least I hope that happens so I can afford to move within 100 miles of the place some day.

Seriously, though, Aspen now requires all new homes to have a balanced whole-house ventilation system with heat recovery that's at least 65% efficient. This is a big deal. Will it be coming to a jurisdiction near you soon? We're in the process of adopting the 2015 IECC now in Georgia, and I doubt we'll go that far. But who knows!

Here's another little confession for you. This isn't the only thing I've kept secret from you. I've got one more big revelation for you about the Aspen energy code, so stay tuned. I'll probably publish it tomorrow. Meanwhile, I've got to start getting ready to go to Las Vegas for the ASHRAE winter conference. Then I'm off to the Spray Polyurethane Foam Alliance Convention before heading home to attend the Atlanta Groundhog Day Juggling Festival. Woohoo! You'll be at all of those events, right?

 

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Comments

Jan 25 2017 - 7:42am

Aspen is becoming well balanced, having both money and sence.

Jan 25 2017 - 8:28am

Excuse my ignorance, but we are not talking about hot-humid climates, right?

Jan 25 2017 - 9:27am

What about people with mold or other sensitivities where pushing contaminants out of the home with pressurization are a good idea?

How likely do you think it is these will be enforced? Blower door testing under 2009 IECC code here in Ohio is seldom used, the visual inspection method is usually used.

Jan 27 2017 - 9:15am

Nate the issue with exhaust only ventilation is that you can't control where the air comes from, thus you cannot ensure it is filtered. With supply only ventilation in cold climates is that it pushes warm "humid" air out where we can't control it increasing the possibilities of it condensing on cold surfaces, which of course wets those surfaces which then leads to rot.

Blower door testing will be used when consumers demand that it is used. The good news is it's pretty easy to say a house that tests at 1 ach50 is better than one that tests higher. The bad news is the average home buyer has no clue about it.

Personally I think every home should have a blower door test as part of the sales inspection process. I bet within 10 years the industry would have a value placed on a lower ACH number per sqft or exterior area that would be pretty realistic.

Feb 5 2017 - 11:36am

Pueblo Colorado has to adapt the newest codes as they come out every year, since we took all the Federal stimulus money we could get (our greedy politicians didn't read the fine print). The new codes are terrible and are designed for one reason, to force the middle class and poor into smaller and smaller homes, and high rise condo's.

Every builder in the County is downsizing and cutting everywhere they can to try to build affordable homes. Our incompetent "city bureaucrats have overreached with economy-strangling regulations", and they are too stupid to know it. We are getting a lot of cool awards though, for being just like Aspen and caring about the planet.

The blower door test should be optional, not mandatory. Did you know that the new codes for 2017 lowered the mandatory 5 ACH to a 3 ACH. Who didn't see that coming? My own home, just completed in December, tested at a 1.8 ACH, but it was expensive to get there. Spray foams, 2x6 walls, tight seals, .30 windows, etc., etc.. I also installed the ERV unit shown above, hooked into my bath fans (no ceiling exhaust holes), and a steamer humidifier, a 97.0% gas variable speed, dual burner furnace, and electronic air filter. And yes, the system is very good and makes the home comfortable. But, I'm spending upwards of 17k for an average 1500sf up/1500sf down SFH home just for the heating/ac system (a standard system 3 years ago was about 7k). Not to mention the additional 5k to 7k for insulation and walls. My savings, you ask, virtually nothing. My gas bill is still around $50 to $75 a month. The 18 year old 1,600/1,600 sf rental home I just moved out of was about $100 to $125 a month. The math: I'm saving about $50 per month x 10 is $500 a year. 20k additional cost/$500 is 40 years. And I'm being overly optimistic regarding my savings. We don't use heat or ac for about 4 to 5 months of the year in Pueblo and I'm not even getting into all the other code changes regarding electrical, plumbing, framing, and the new "residential fire codes". And all of this because of global warming.....uh,,,er, cooling....., uh eh,, I mean climate change.

And incidentally. Buying a home in Aspen or Vail is not an option for 97% of the population. I can't even afford to ski there anymore. The wealthy can spend whatever makes them "feel good". Us peasants have worry about paying the bank back. Great article.

Feb 6 2017 - 3:17pm

@Chris, interesting comment. There are reasons other than building codes why homes in places like Aspen and Vail cost so much. Nevertheless, I do agree that mandatory balanced ventilation is overreach.

OTOH, your mechanical budget can easily be pared from $17k. In particular, code doesn't require a 97% dual capacity furnace with variable blower. For the reasons you stated (irrational payback), I specify the least expensive two-pipe (90%) single capacity furnaces for most of the high performance homes I work on. In my experience, anything more than that isn't justified based on efficiency. Moreover, humidifiers aren't required by code, and in fact should not be necessary to maintain 35% to 40% if house is tight. And finally, getting to 3 ACH50 needn't add much cost, especially in markets where blower door testing is mandatory. I own a production built home cira 2005 that tested out better than that.

Feb 7 2017 - 2:37pm

Chris, with the the expense of foam, spraying it in walls make little to no sense. Especially open cell. Open has a R value less than cellulose. If the cavity is filled it does not meet the code in a 3.5" cavity. I have an insulation company in South Central Georgia. We commonly get 2.5 -3.5 ACH. No foam. I say this a lot...If I can give +/- 3ach, good R value with spray applied cellulose, why would someone want to pay twice as much for the same if not slightly better? I have a foam machine. I'm just honest. We did a man's home hear several years ago. I was with him back in the spring and asked him about his bill on the house. He showed me the previous years or more bills. They averaged under $200. Not bad for 8200 sf, 3 HVAC, 2 story, electric water heating, No foam!!!!

Jan 25 2017 - 9:28am

Interesting stuff, Allison. Based on a quick glance at the ERV/HRV listings in HVI, it looks like roughly 25% of the listed units DO NOT meet 65% SRE at their rated airflow.

In addition, some of the units that DO meet 65% SRE are doing so only at a relatively low airflow and won't take the cut at higher airflows.

Jan 25 2017 - 9:47am

Is it conceivably easier - and less expensive - to achieve balanced ventilation with a tighter-than-normal house? Or does that bear only indirect or even no relation?

Jan 27 2017 - 1:25pm

IMO it is the amount of leakage found in ducts which are located in vented attics that will determine how difficult it is to balance ventilation. Leaky ducts in vented attics will suck in exterior air via cracks in the house.

There really are only two downsides to building a balanced ventilation system. #1 Higher upfront cost, dedicated supply/exhaust ducts along with the ERV/HRV itself is expensive (ex Zehnder). #2 Occupant behavior, the average homeowner must take time to service the system (ie. replace filters, etc) and understand what the system is/is not designed to accomplish.

Something to keep in mind with regards to mechanical ventilation. Mechanical ventilation became the solution to IAQ problems which appeared when building codes required tighter homes.

Jan 25 2017 - 11:14am

The use of balanced ventilation should be mandated in many homes that have hydronic heat (Used in Aspen and the West) to clear contaminates. This will improve the Indoor Air Quality for this heating system use versus forced air heating and allow some internal moisture removal. Too often people think that what ventilation system used in other areas of the US also applies to every part of the country. Hydronic heating can provide a more efficient system than just accepting the next available forced air unit.

Jan 25 2017 - 11:39am

You need to review Minnesota codes more. Balanced ventilation has been in place here for almost a decade (we did have an exception for exhaust only though, until 2 years ago. Now balanced is required)

Jan 25 2017 - 12:01pm

With hydronics how do you decide on an HRV or ERV if your winters are extremely dry and your spring and summers are very humid? We have to run a humidifier all winter and a dehumidifier all spring and some of summer. I don't see how you make it work.

Jan 25 2017 - 4:27pm

Tom in creating a very energy efficient home I learned that two people can charge the interior humidity to 50% even when the exterior humidity is 20 to 30%. By moving the air and exchanging with exterior air it has been possible to lower the overall interior humidity to a more balanced 25 to 35% increasing the environmental air quality and removing smells. I am using a heat recovery ventilator and our biggest problem has come from the winter cold at night when the temperature is below -10F for an extended period. Humidity can be added or removed with the correct equipment.

Jan 25 2017 - 7:29pm

Thanks for your input --please see my reply to David Eakin below.

Jan 25 2017 - 12:18pm

My problem with the ASHRAE mandate is that it is unproven - both in every locale and in principle. Where are the quantified studies that show measured reductions in defined/universally-adopted contaminants? Where are the studies that show ERV/HRVs remove more of these contaminants than a recirculating ventilation system with HEPA/activated charcoal filters? Where are the installed contaminant alert systems that show residents that they are living in environments with good IAQ? The whole principle of HRV/ERVs is that outside air is much less contaminated than indoor air - a dubious assumption. It's the same principle that drives Passive House design to have user-openable windows (which compounds their price compared to fixed units). There is one proven comfort "goodness" about using ERV/HRVs (and recirculating systems) - temperature stratification reduction. But then the argument logically follows that prescriptive shell R-values are developed assuming stack effect air temp stratification (which these systems eliminate).

Jan 27 2017 - 8:21am

HRV/ERV's contain better than average filtering systems. Their purpose is to filter outside contaminants before they enter living spaces.

Jan 27 2017 - 8:37am

"The whole principle of HRV/ERVs is that outside air is much less contaminated than indoor air - a dubious assumption"

Actually there are a plethora of studies proving indoor air is much dirtier than outdoor air. Some examples of well documented indoor containments: Pollutants from cooking especially those which burn a fuel (i.e. NatGas, Propane). Cleaning chemicals. Chemicals and outgassing emanating from carpeting and furniture. Chemicals which leaking into the home from an improperly air-sealed attached garage. Chemicals/pollutants brought into the house.*

*Back in the day when asbestos was widely used it was discovered that children who developed asbestos related problems had inhaled fibers that mom/dad tracked into the house.

Jan 27 2017 - 11:53am

I think you need to re-check your sources. I found this after a 1 minute search: http://www.lung.org/our-initiatives/healthy-air/sota/city-rankings/most-.... And this does not go into details about the air pollution found in many metropolitan areas (let alone huge problems in India and China). Again, if you are not measuring (and do not have a standard as to WHAT you are measuring) it is hard to prove that any locale or setting (indoors/outdoors) or remediation method actually is improving IAQ.

Jan 27 2017 - 12:56pm

Your link referenced is essentially irrelevant because it only ranks air quality of cities and does not distinguish between indoor/outdoor air quality. Google located these and many more results.

https://www.epa.gov/indoor-air-quality-iaq/inside-story-guide-indoor-air...

http://teachersinstitute.yale.edu/curriculum/units/2011/4/11.04.02.x.html

http://journal.frontiersin.org/article/10.3389/fenvs.2014.00069/full

http://www.cnbc.com/2016/04/22/indoor-air-can-be-deadlier-than-outdoor-a...

Jan 30 2017 - 10:17am

Kris - all your sources agree with my original statement - that outside air can be (and often is) not of good quality; that many indoor air quality issues are generated from outdoor air infiltration (in addition to smoking and cooking with coal or other non-exhausted combustibles); that there are currently no good means for definitively/consistently/affordably measuring indoor air quality; that there are several different interpretations of what constitutes "good air" (or "bad air"). Again, unless there is definitive, universally-accepted testing of IAQ prior to any remediation action followed up with continual post remedial action no one can say with any certainty that a situation was "bad" to begin with, has been improved, or stays "good". Certainly not by installing an expensive mechanical ventilation system that assumes outside air is "better" than indoor air - "just because"; without any pre/post/continual testing.

Jan 31 2017 - 10:53am

"Again, unless there is definitive, universally-accepted testing of IAQ prior to any remediation action followed up with continual post remedial action no one can say with any certainty that a situation was "bad" to begin with, has been improved, or stays "good". "

You're saying remedial action as in remediation (ie. renovate). I'd agree that it may be difficult to measure the degree of improvement in say a leaky (pre-2009?) home prior to and after the installation of a mechanical ventilation system.

For a newly built tight house the benefits are indeed measurable. After all it doesn't take 100 percent measurable certainty to know that IAQ is substantially better when the supply air is pulled through a MERV 7 or better filter vs the supply air gained by opening a window. In any case IAQ aside, a tight house requires mechanical ventilation for owner comfort and the prevention of interior rot due to high levels of humidity. Opening a window adds an energy penalty which goes against the purpose of requiring tighter building envelopes to begin with.

You can always visit Building Science Corporation for catalog of reports and studies on the matter.

Here's a little taste: https://buildingscience.com/documents/bareports/ba-1309-ventilation-syst...

Jan 25 2017 - 1:36pm

@Nate, why would balanced ventilation be any less effective than exhaust ventilation in removing contaminants?

Jan 27 2017 - 8:19am

Exhaust-only pulls air through voids in the building envelope therefore it's not filtered air.

Jan 25 2017 - 1:59pm

Tom wrote: "I don't see how you make it work."

Why do you say that?

BTW, I consider humidifiers and dehumidifiers to be relics of the past - nothing more than expensive band-aids (in most cases).

Fix the problem, not the symptom. Clearly, the best defense against winter dryness and spring/summer humidity is to keep out the outside air.

Some mechanical designers routinely install dehumidifiers in low-load homes, ostensibly because a much smaller cooling system can't handle the latent load. That's nonsense. If a high performance home requires supplemental dehumidification, it usually means something is wrong... over-ventilation or ventilating without enthalpy exchange, improper mechanical design, leaky envelope, improper use of spot ventilation, etc.

As for HRV versus ERV... an HRV would only exacerbate the conditions you describe. OTOH, an ERV acts to keep moisture in when it's cold and dry outside, and keep moisture out when it's warm and humid outside.

Jan 25 2017 - 7:27pm

I am thankful for any advice. I am not an HVAC expert but a mechanical engineer and occasional residential architect. It would be great to avoid humidifiers and especially dehumidifiers. When I first started designing this house for us 10 years ago I was going to install an HRV with balanced ventilation as humidity was rarely a problem and only short term and I was looking strictly at efficiency. (I didn't look much at ERV's so was not aware they would reduce air dryness in the winter.)

At the time we were in the old farmhouse built in 1928. A Sears kit house - very well built structurally - energy efficient not so much. You couldn't keep that house with central heat warm in Eastern Montana winters -- -30-40F for days and 20-30MPH. But in the summer we could "Texas cool" - open the windows upstairs and down and run two 20 inch box fans all night. House was comfortable all day.

So we built these things into the design of our new house changing the central heat for hydronics but still no A/C and no intention on putting it in. But the weather has changed - we have not been able to use the whole house fan to cool this house due to the now high spring and summer humidity. We now routinely get fog at night at 50-60F.

This house is 2000sqft with full finished basement and just my wife and I living here. It is well insulated all round with vapor barrier inside and Tyvek outside. For now we have exhaust only ventilation provided by a radon mitigation fan (intake thru four exterior doors and masc. leakage). (I find door design and construction unbelievably poor.) Two years ago we had to start using the dehumidifier. I have avoided the balanced ventilation question because I don't know how to deal with the humidity extremes.

I would like to be convinced that an ERV would eliminate the need for the humidifier and dehumidifier.

Jan 27 2017 - 8:26am

In mixed-humid and humid climate zones dehumidifiers are needed during the shoulder seasons when neither the heat nor the A/C is operating. A ERV, depending on the temp differences and humidity levels between the inside and outside of a house can reduce interior humidity, but an ERV does not function as a dehumidifier.

Jan 26 2017 - 1:27am

@Tom, since the whole-house fan won't cool the house, how are you keeping cool? A small mini-split in the family area or bedroom would kill two birds. Without A/C, it's hard to say if an ERV would keep RH under control in warm weather. It's going to depend on how much of your latent load is from ventilation versus infiltration. An ERV reduces the former (by roughly half) but does nothing remove moisture from infiltration (or internal loads).

You didn't mention if you need to use a humidifier in your new home in winter, but an ERV would recycle some portion of internally generated moisture. Whether it's enough to avoid using a humidifier depends on how tight your envelope is, and your ventilation rate.

FYI, latent efficiency of an ERV depends the delta-DP (dew point) between the two air streams. The drier the outside air, the more interior moisture gets passed to the incoming air stream, the exact opposite of what happens in summer. This isn't a special operating mode, it's just the way an enthalpy core naturally works.

Here's a tip... Since moving to Arizona, I learned that by not using spot exhaust for showers and cooking (when exhaust is only water vapor), I can improve humidity levels in dry weather, which is most of the year.

Jan 27 2017 - 3:22pm

If the shell is tight, supplemental dehumidification usually isn't needed. I've designed mechanicals for dozens of projects in humid climates like Alabama and Florida over the years. The only time I recall specifying a dehumidifier was for a rental property at the beach. The key is to build tight and keep ventilation to a minimum. Homes that are leaky and/or over-ventilated may need a dehumidifier.

Before moving to AZ, I lived in Charlotte where it wasn't unusual to have periods of mild & rainy weather, especially in Spring. My home wasn't nearly as tight as those of my clients (~5 ACH50, 3,200 ft2) and even then, RH rarely exceeded 60%. My cooling costs averaged well under $200/yr (I had my heat pump submetered). A dehumidifier could easily increase that by 50%!! Ideally, you want to keep RH below 60 for comfort but brief excursions into the low 60's don't pose any durability or mold risks.

Jan 26 2017 - 5:36pm

Hi David, Until last year cooling was not really an issue -- the house has a full wrap 8ft porch and summers have been cooler. However my wife has COPD and started finding warm air uncomfortable so we bought a Whyter 14kBTU portable. I did not have high expectations -- but we both ended up STUNNED at how well it works and it is much less costly to run than expected. The house is pretty open plan with large open stairwell.
We have always had to use humidifiers in winter in Montana. It is a simple Bemis used upstairs and we push about 3 Gal into the air every day. The small dehumidifier is run in the basement. When used these three appliances are run only during the day. It is extremely dry here in winter -- it snowed three weeks ago and the snow is still powder and the sun has been out for days.
From yours and the rest of the comments in this post it doesn't sound like I'm going to be getting rid of the any of them. I will switch to an ERV to hopefully reduce the use of them.

Jan 25 2017 - 6:45pm

I would not put too much credence on what ASPEN does as it is not an indication of what the ICC will do. The Home Builders will make sure that all three options are still available. ASPEN is an out lire and Joe L winters there and has the ear of the Building Official so the country is not going the same direction as ASPEN.

Jan 25 2017 - 10:11pm

Good discussion folks. Much of Canada has a balanced ventilation requirement and it is not as expensive as some would believe. In the order of $800 to $1200 incremental over the supply air or exhaust only that are common. This presents a very attractive ROI in most markets at current interest rates. As for the need for ventilation and the right rate, there have indeed been studies done on this or at the very least good history of success. I have articles from the early 1900's on ventilation and tuberculosis. Health Canada has done a few studies on this as well. We have even better data on ventilation rates for pigs, chickens and cows of course, because there is money associated with those.

Jan 26 2017 - 11:52am

Minnesota requires balanced ventilation, but it does not require heat recovery. Most builders are installing HRVs.

Jan 26 2017 - 4:28pm

I love this blog site. Especially since ventilation and moisture control are discussed so frequently. Allison, I am pretty sure you purposely bring up this topic in perfectly timed intervals, just to keep junkies like me tuned in. Thank you. I love to keep up with all the opinions.
Continuing the trend, here are yet a few more opinions.
1) I hope they do not mandate balanced ventilation for the sake of the "balanced". In humid climates, this causes manufacturers, builders, designers, and HVAC providers to promote, believe in, rely on, charge for, and put total faith in, ERVs. Too many people in this business think that this device will address the increased latent load from ventilation. It does not. For summer moisture control, ERVs are overrated. More on this in a minute.
2) Ventilation mandates for the future are inevitable. I do not disagree with the benefits of outside air. I love the windows down in my car. But mandated, specified volumes of outdoor air without regard to summer moisture consequences will get us all in trouble, regardless of balanced or otherwise. If you want to mandate xxx cfm without regard to outdoor dew point, you are forcing me to condition this air.
3) A long time ago, the fresh air leaking into a home or being drawn into the home when the clothes dryer ran was not as much my responsibility as it is now when my ventilation strategy is purposely bringing in xxx cfm of humid air. Now, I own this air and whatever is in it.
4) Maybe the most important consideration... a perfectly sized AC is very likely not adequate for proper dehumidification, especially (maybe whenever) mechanical ventilation is utilized. When the AC runs, it can be extremely effective. But when it don't run, it don't dehumidify. I keep track of this and many of our energy efficient homes do not have adequate AC run time for several days. If you are bringing in 70 degree dew point air during low AC run times, you will need supplemental dehumidification.
More on ERVs. A standard ERV will remove about one third of the moisture it brings in. This is a best-case ratio. So, for every 3 parts moisture you bring in, you net 2 parts added to the indoor humidity. During low AC run times, continued ventilation continues to raise the indoor humidity. This makes the ERV even less effective. You are gradually losing your dry air from inside and this is the "tool" to pull moisture from the incoming air. Soon you flood the home.
Summary. If you must mandate ventilation, fine, but somebody now owns this air and anything in it. If I own it, I will install the vent, ducting, damper, controller and the dehumidifier. These items are now the base cost. If balance ventilation is mandated, this cost is on top of my base cost and it's starting to get expensive.

Jan 26 2017 - 7:51pm

You are an idol. I shared this on my facebook page with the comment: "Can anyone remember a time when once outside, you LOVE how the air smells? That,is telling you something!"

Jan 26 2017 - 8:01pm

Did they copy that clause from the 2014 VBBL, even down to the CSA test standard?

Jan 27 2017 - 8:08pm

While I appreciate codes requiring higher quality / more energy efficient systems I am skeptical when it comes to enforcement. Will these systems all be commissioned? By who? What credentials must those commissioning agents hold? What tools must be used to measure airflow, etc? Who does QA on those agents? What happens when a system is installed so poorly and can't be balanced? These systems are complex enough that without the type of enforcement I described we're just going to end up with a whole bunch of HRV / ERV's using energy 24 hrs a day until the homeowners figure out a way to turn them off.

Feb 5 2017 - 12:24pm

The Federal Government is forcing Builders to install more and more complex and electronically controlled systems that are susceptible to electric surges and power drop offs. All of this junk will fail after several years and few people will spend the time and money to fix it. In the real world, I still can't get most of my home owners to even change their furnace filters! So what's next, government inspectors sent into everyone's homes to "verify" that they are keeping their system serviced and thus, energy efficient in order to save the planet and the children? They are already talking about sending in government inspectors to check the fire sprinklers and smoke alarms like they do on commercial buildings.

Feb 8 2017 - 12:56pm

Agree 100%. Occupant behavior is a wildcard.

Feb 6 2017 - 8:17am

As one who strongly feels there is way to much Government in our lives why not just leave this balanced air concept up to the home owners?

Feb 6 2017 - 11:06pm

I can't wrap my mind around residential opening up a passageway for outdoor air to come in, in ANY climate when a mechanical air conditioning system is working... If you are heating it is because it's cold outside, if you are cooling it's because it's hot outside... the whole idea is to be different that what it is outside... This is the beauty of NOT AIR TIGHT Homes... The air that DOES get in and it WILL get in, is limited to what is necessary, and it is filtered through the various, well spread out and minute leak spots in the home... Is that NOT energy efficient, yes, but is the extra cost of conditioning the leaked air worth the extra costs of actually conditioning the undesirable outside air in equal porportion to the conditioned inside air... makes no sense to me... But even if I'm too stupid to understand it, why not just defy Dad and open a door or window... If this is about indoor air quality, surely there are enough nice days everywhere to air out the home once in a while...

Feb 7 2017 - 2:52pm

@Bob, to the extent that you're talking about energy costs, your comment makes no sense. The cost of heating or cooling ventilation air is the same as heating/cooling air that leaks through the shell. The difference is, if you build NOT TIGHT as you suggest, you have no control over how much air leaks, and thus must be conditioned. It makes more sense to build tight and then limit the volume of outside air via a designed system. You can always turn off the ventilation system on 'nice days' and throw open those windows!

I do agree with earlier comments that the type of ventilation system should be left up to the designer, builder or homeowner as the case may be.

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