Comments on: Residential Ventilation Smackdown — The Battle Over Simplicity

By: Dave Eakin

Dave Eakin — Wed, 20 Feb 2013 03:49:17 +0000

I would love to see the
I would love to see the following theory proved/disproved: air follows the path of least resistance; mechanical ventilation (provided for each living space and engineered to meet the current ASHRE guidance) will be that path of least resistance so there will be no "natural infiltration".

By: TedKidd

TedKidd — Sat, 02 Feb 2013 10:45:57 +0000

Leakage as a proxy for fresh
Leakage as a proxy for fresh air? Maybe if you have no experience testing IAQ over time. But its little better than measuring my feet when sizing for gloves.

Some tight houses have great iaq, some lose houses have terrible iaq. A blower door measures tightness, not air quality.

Changing rules that take pretty long leaps of faith wrt what is accomplished seems pretty crazy. These programs are really fully burdened, seems adding straws is reckless and myopic at this point! Who benefit$ from such things?

Certainly not the consumer. Change adds cost in training, may add cost to the consumer beyond the imbeded employee cost, and may simply mean much smaller dispersion of better practices as more turn their backs to this stuff.

This argument will hopefully be mute shortly. We will have devices that MEASURE air quality. Shortly following these devices will control your ventilation (is becoming more common to use expensive CO2 monitors for control now, though I'm not convinced CO2 levels are great proxy for IAQ)

In the meantime, always recommend mechanical ventilation to your clients. Get them used to the idea houses need fresh air, and cya in the event it is later discovered their air quality is a problem.

By: Clayton DeKorne

Clayton DeKorne — Mon, 21 Jan 2013 21:02:40 +0000

It might be useful to focus
It might be useful to focus the fight in the retrofit/weatherization/home performance arena? 62.2-2010, of course, covers both new construction and existing homes, but is it really that complicated for new construction? The requirements for existing homes, however, is much more awkward and leaves room for further development.

Take just the calculation of the ventilation requirements for existing homes. The big-picture approach is better than BTL (I agree with Bill Smith here; leaving behind the BTL is certainly a positive step forward). But the calc for existing homes, while maybe not a CYA approach, still seems full of compromise.

This is my take on the procedure for existing homes:
1) Calculate an initial rate for the whole-building ventilation requirement.

2) Determine what is required to meet local exhaust ventilation requirements.

3) Adjust whole-building requirement to accommodate existing local exhaust:
--Add up local exhaust deficits (including any window credits).
--Divide combined deficits by 4.
--Add this amount to the initial whole-building requirement.

4) Find Natural Infiltration (ICFM)
--Run BD test to find initial CFM50.
--Convert CFM50 to ICFM using appropriate weather factor.

5) Calculate infiltration credit, using the formula: 0.5 (ICFM – 2 CFA/100)

6) Determine required whole-building fan capacity by subtracting the infiltration credit from adjusted whole-building requirement.

It's the adjustment of the whole-house ventilation to accommodate existing local exhaust (step 3 above) and calculating the Infiltration Credit (steps 4 and 5) that is the awkward part.

By: Ryan Shanahan

Ryan Shanahan — Sat, 19 Jan 2013 05:09:46 +0000

I assumed the &quot
I assumed the “ventilation battle” would be about the 4 different types of ventilation: a) exhaust only – easy to build in, but does it work well? b) supply only – more complicated to build in, can lead to comfort issues in shoulder months, c) balanced – combines supply and exhaust, d) balanced with heat recovery – most expensive, hardest to implement, most efficient.

By: Bill Smith

Bill Smith — Fri, 18 Jan 2013 21:44:28 +0000

Wow, I'm glad to see that Dr.
Wow, I'm glad to see that Dr. Joe agrees with me on residential ventilation ;~)

One of the dumbest things that ever got promulgated to the residential building science field is the BTL. It is a classic CYA attempt which does the occupants of a building no real good.

Repeat after me: This house needs a ventilation system. That house needs a ventilation system. Every house needs a ventilation system.

Sizing is more complicated, but not much. Low level continuous at something below the ASHRAE standard (Gee, 60% sounds reasonable) with spot ventilation for high load areas: Kitchens, baths, rooms with 15 aquariums.

Not that I have an opinion on this...

By: Allison Bailes

Allison Bailes — Fri, 18 Jan 2013 20:50:51 +0000

Don P.: As
Don P.: As Dave Eakin said, attic ventilation is a whole different animal, an important one, to be sure, but outside the scope of what we're talking about here.

Nate A.: As Paul pointed out, 62-89 wasn't as simple as it's made out to be, and 62.2-2010 isn't as complex as it's made out to be. You're right, though - A lot of the problem is because people don't like change.

Dave E.: Indeed, Joe and BSC are spot on by claiming that we need to stop trying to use a blower door to figure out how much ventilation we need. As he says, "To me, the ventilate right part is easy: put in a ventilation system and pick a rate." See footnote 4 in his article Just Right and Airtight for the details of how BSC does that. I'll write more about this issue in another article because it's a big, important topic.

By: Dave Eakin

Dave Eakin — Fri, 18 Jan 2013 20:15:36 +0000

To Don – do not confuse
To Don – do not confuse indoor ventilation (the subject of this blog) with attic ventilation. If you reduce interior air leakage, attic ventilation becomes a minor issue while indoor ventilation becomes a major issue.

Allison – don’t want to get into a battle of the Titans, but another Titan – Dr. Joe – has recommended for quite some time not to get tied up with the “seal it tight and ventilate right”; just “ventilate right”, which I interpret as every home needs proper ventilation by intentionally providing it rather than relying on unintentional ventilation (cracks/gaps through dusty/moldy areas) and that this design aspect might be as/more important than air sealing.

By: Nate Adams

Nate Adams — Fri, 18 Jan 2013 19:55:37 +0000

I'm glad I'm not trying to
I'm glad I'm not trying to keep these guys apart! While I sometimes get a little annoyed with auditors and experts discussing everything ad nauseum (as a contractor I just want to get in there and FIX it!), as a closet egghead, I'm really glad to see the discussion. This leads to better solutions and it's fun to watch the blow by blow.

I appreciate Krigger fighting for simplicity because the changes make contractors' lives a bit hellish. As usual, the solution is probably in the middle, John had a hypothesis, Paul the antithesis, and the synthesis should turn out well! It's good to really like both fighters too!

By: Don Peek

Don Peek — Fri, 18 Jan 2013 19:52:06 +0000

Thanks for timely post on the
Thanks for timely post on the hot topic of ventilation. For attics a Hip Ridge vent systems can add much needed NFA (attic exhaust). It's a bit risky and can be a tough install on rerto.