https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/ Building science knowledge, HVAC design, & fun Thu, 29 Jul 2021 14:34:42 +0000 hourly 1 https://wordpress.org/?v=6.6.2 https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6915 Mon, 20 Oct 2014 02:52:32 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6915 What are your thoughts on
What are your thoughts on whole house air purifiers?

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6914 Sun, 06 Apr 2014 19:30:31 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6914 It always has and always will
It always has and always will be more lucrative to treat symptoms than to solve problems, ask the pharmaceutical industry! 
 
ASHRAE 62.2 seems to be effectively a one size fits all treatment of what are a myriad of problems, their infinite number of combinations & symptoms they produce.  
The issue that Cinderella’s sisters had with wearing her shoe was that it gave some bunions, others blisters & some both. That’s an old story & this approach will someday be seen as incredibly primitive and myopic. 
 
Until the problems/causes of symptoms are identified and understood solutions are a guess. 
Every locations exterior air quality varies seasonally, even hourly. 
Every building interior air quality varies by occupancy, interior finishes, furnishings, equipment. 
Some of these varying conditions produce problems which require filtration &/or ventilation. Given the exterior & interior variables the need for filtration or ventilation varies. Note that the nature of output of VOCs (one of the polluter types of greatest concern) is high after manufacture and lower as times passes.  
Air quality may be improved best & most efficiently by operating ventilation from ‘low to high’ or to preserve it by turning ventilation off. 
 
I submit there is no way to avoid the blisters (under achieving good air quality) & bunions (driving the cost of construction higher and further from reach of more and more people with little return) with a one size fits all approach. 
 
I wish far more time was spent understanding, measuring & mitigating the problems individually than trying to find the right shoes size. 
There’s more money to be made in doing & redoing the latter and it is a far steeper hill to climb to do the former.  
 
Reliable protocols & standards to measure the risks for each potential air quality defect inside & out are needed. 
Devices to monitor air quality for these defects inside & out are needed. No the plural, devices! 
Until then prescriptive ventilation and filtration solutions are a “try this & call me in the morning approach”, read GUESS. 
Primitive is only one word that describes that! And yes, lucrative is another!

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6913 Fri, 28 Mar 2014 02:01:54 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6913 David 

David 
Thanks. If we see this problem every 15 years, I can live with that.

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6912 Thu, 27 Mar 2014 23:50:00 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6912 @Ed, this was clearly a
@Ed, this was clearly a winter RH problem as noted in my previous comment. I can’t see how mold could form in those locations in summer.  
 
The fact that you haven’t seen this problem (yet) doesn’t mean much. If anything, the risk would be higher in colder climates. Again, it all depends on convergence of several factors – envelope tightness and size, amount of moisture generated and temperature variations. Voids in wall insulation could certainly be a contributing factor to the latter.

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6911 Thu, 27 Mar 2014 16:16:27 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6911 David: 

David: 
Thanks. 
Is it a winter or summer problem? If winter, could the mold behind the furniture be due to high RH plus maybe weak insulation in the wall?? If the house was built so recently, then maybe not. 
I am soooo glad we don’t have to deal with that a couple of hundred miles north of you.

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6910 Thu, 27 Mar 2014 12:34:05 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6910 @Ed, my brother lives in
@Ed, my brother lives in central NC (CZ-4A). Although I don’t know the R-values or blower door results, his envelope and mechanicals were engineered and verified by a energy efficiency specialist (cira 2000) whose name I will not mention. The ERV is a Honeywell with enthalpy wheel. The two exhaust inlets are in the baths. His shower has two heads, with non-code flow rates. Lots of steam.  
 
Mold remediation was expensive because of the extent of the damage. I think he overpaid, but that’s another story. He had to move out for about a week as I recall.  
 
He did not take my advice, to install a dedicated bath fan. Instead, his mechanical contractor reconfigured his heat pumps as dehumidifers on RH calls. He has a Voyager water heater and hydronic supplemental heat fan coils, which made it simple to use them for reheat. But his gas bills last summer were higher than his typical winter gas bills! The problem with that is that the mold manifested mostly on walls behind furniture and in closets with exterior exposure, which clearly indicates high winter RH. 

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6909 Thu, 27 Mar 2014 12:13:19 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6909 @Rob, an ERV system
@Rob, an ERV system (including controls) can certainly be designed so that recycled moisture doesn’t lead to unacceptable RH levels. But we must first recognize the potential problem. Otherwise status-quo installation practice exposes super-tight homes to this poorly understood risk. 
 
I have a client in northern Maine at present who’s building a home to near-passive house standards. He intends to use 2 ductless mini-splits for h&c; and a (ducted) recovery ventilator. This issue (ERV vs HRV) came up in a conference call last night. With an envelope approaching 1 ACH50, an ERV will no doubt raise RH by recycling perhaps 50% of internally generated moisture. This is uniformly considered a benefit of using an ERV in cold climates. 
 
Here’s the problem in homes like this… During the coldest weather he can expect significant temperature variations in bedrooms and other isolated areas such as closets. This is an acceptable tradeoff to folks wanting to take advantage of low cost and high efficiency of ductless heat pumps. So with a family of 4 in such a tight enclosure, the question we pondered is whether the recycled moisture would be enough to create mold-producing RH in nooks and crannies that don’t receive direct supply air from the heat pump. The truth is, I don’t know the answer, but based on simple psychrometric analysis, this home seems to be a high risk if he relies solely on an ERV to exhaust the baths. I recommended two options: install dedicated bath exhaust fans or go with an HRV and forfeit more comfortable RH levels. Perhaps I’ll suggest your approach (multi-speed ERV) as a 3rd option. 
 
Thanks for the conversation.

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6908 Wed, 26 Mar 2014 17:22:48 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6908 David: 

David: 
Could you tell us a little more about the problem in your brother’s house? 
What climate is it in? How much insulation is in walls and ceilings? What is the Infiltration rate? Where did the problem manifest? What was the repair that cost so much? Was the repair successful? 
Must be lucky, but here in the mid-Atlantic we haven’t seen this sort of thing. 
Thanks 

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6907 Wed, 26 Mar 2014 17:05:00 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6907 that’s valuable feedback,
that’s valuable feedback, thanks David. your ongoing engagement and contributions to the industry and my personal education are always appreciated here. 
 
Given the issues I’ve seen with HRVs, I think my initial response would be that your statement is a fine argument for a humidistat control on the ERV to ensure it is run properly. I find it… unlikely… that any commonly sized ERV would be incapable of removing enough moisture to prevent mold if controlled adequately. 
 
But, as I continue to noodle this, I realize that my experience is also primarily with homes involved enough to higher a specialty mechanical designer… and the ventilators have always been sized to exhaust multiple baths at once on a high speed setting with intermittent or continuous low speed as the baseline operation, so the problem is reduced to basically only “how much do we have to run at high speed to reduce the moisture”.. we’re simply not going to exceed the max cap of the ERV to remove moisture.. if we did, even individual bath fans wouldn’t be adequate anymore (the ERV has at most 60% exchange efficiency remember). but in other homes with smaller ventilators sized for IAQ only I could see how that would not be true. 
 
I’ve learned something today, great way to start the day. thanks David. I do wish the statement about ERVs and baths were slightly more nuanced though. ERVs with high rate exhaust capacity… and a dehumidistat controller!… shouldn’t be a problem anywhere if controlled properly. it seems that the issue should, as I currently understand it, only really apply to homes with minimally sized/fixed speed units.

]]> https://www.energyvanguard.com/blog/the-ventilation-debate-continues-interview-with-dr-iain-walker/#comment-6906 Tue, 25 Mar 2014 23:27:28 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-ventilation-debate-continues-interview-with-dr-iain-walker#comment-6906 @Rob, whether or not this
@Rob, whether or not this ends up being a problem for any given home depends on size of home, how tight it is, the amount of moisture generated, and temperature variations within the home. These things cannot be modeled or predicted so the prudent course of action is to avoid the risk. 
 
This risk is not just theoretical. For example, my brother’s home had an ERV as the only exhaust in master bath. His home is not small but he has two shower heads. He recently had to spend ~$20k for mold remediation. The nominal RH during winter was as high as 50%!  
 
I’ve read other anecdotal reports of tight homes with winter RH issues due to inadequate bath exhaust. The mold show typically shows up in closets with exterior exposure and behind furniture due to imperfect heat distribution. 50% RH can easily become 70% in those areas. 
 
Since the designer has no control over how much moisture a family generates or how they manage temperature settings, it seems prudent to be conservative here, even if the problem only manifests in a small percentage of homes. If course, if an individual designer understands the issue and is confident enough in his or her assessment and willing to assume the risk, then fine. But most ‘green building’ specifiers are not qualified to do this sort of analysis. So I think there’s an obligation to push back against mainstream practice when risks like this are uncovered. 
 
BTW, Panasonic WhisperComfort prohibits installation in laundry or baths. As homes become tighter, other ERV manufacturers would do well to follow Panasonic’s lead.

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