[Greenbuilding] insulation vs. air sealing

[Gennaro Brooks-Church]

Ventilation in a well sealed house is not just for humidity. Seeing as
the body releases all sorts of nasty toxins you are also ventilating
for that. For example studies show that CO2 levels get really high in
bedrooms at night.

Gennaro Brooks-Church

Cell: 1 347 244 3016 USA
www.EcoBrooklyn.com
22 2nd St; Brooklyn, NY 11231




On Mon, Oct 4, 2010 at 8:16 AM, Brian Uher <brian at amicusgreen.com> wrote:
> Hi David-
>
> It seems that the time to ventilate is when you need to evacuate moisture.
> You need to evacuate moisture when it builds up or when it's new equilibrium
> is above the holding capacity of the materials - when the settling point
> supports mold growth.
>
> Winter air is dry, so ventilation is not needed in winter-as it warms, it
> gets even drier, relatively speaking.
> But keeping interior vapor out of the attic is critical.
>
> Summer air is humid, but if the attic matches the temperature of the
> exterior, the humidity matches as well.  Condensation does not occur, so
> accumulation of moisture in the wood should not occur.
> But keeping the interior cooling (both via exfiltration and conduction) out
> of the attic is critical.
>
> So, maybe you really never need ventilation but always need airflow and
> thermal flow control.
>
> The one exception: rain penetration will wet the wood.  But that situation
> is catastrophic and a repair since it means your design sucks or your roof
> is leaking.
>
> Thoughts?
> -Brian
>
>
> On 10/3/10 11:09 PM, Futureship wrote:
>
> Good question ? What are the conditions in the attic that would
> Merit ventilation after air sealing
> And insulation ?
>
> On Oct 3, 2010, at 1:27 PM,
> David Wentling
>
> "With the airseal measures in place, and the moisture contribution from
> ex-filtration to the attic eliminated, the question is do you need to
> ventilate?"
>
> David Wentling
>
> From: Futureship <futureship0000 at hotmail.com>
>
>
> I have a question with regard to
> Your results:
>
> In the first case you described that "Results were 15% higher energy usage
> with
> 10% greater leakage."
>
> How does a blower door measurement
> Tell you 10% greater leakage? The
> Blower door measures holes in
> The building envelope . Assuming no
> Air sealing was done the blower door
> Would not measure a 10% greater leakage. I would argue the increase in stack
> effect In this case caused an increase in pressure thru the same holes
> therefore
> causing more airflow thru the same holes.
>
>
>
>
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