Do it Yourself: [DIY] Re: Just an after thought:

15 January 2013

[DIY] Re: Just an after thought:

Posted by: "Dale S" dalu@hbcomm.net

> While watching an episode of "This Old House" last night I
> noticed they now have a new structural integrity test that they
> can run on a completed home. In this instance an exhaust fan
> was installed in the front doorway and the CFM of the exhaust
> air was measured to determine how draft tight the overall
> structure was.

Hi Dale;

That is a standard blower door test. You can get them
most anywhere. A lot of utilities even conduct them.

> This was a large three story home with a full basement
> and they drew less than 2,000 cfm which is pretty low.

They are usually rated at ACH (air change per hour) @ 50 PA

> This tells me that the natural flow of fresh air through that
> house with all the windows and doors shut in the fall and winter
> months would be like living in a walk-in refrigerator with a
> furnace.

Lets see. The house seems to be maybe 1000ft²/story
with 2½ stories, plus a basement, so maybe about
28000ft³ per AC If it leaks 2000CFM @50PA that
would be about 120000CFH, and 4.3ACH @50PA
which may be alright for a remodeling, but is not at all
impressive, by modern energy efficient house building
standards. For instance, the Passive Haus maximum
standard is 0.6ACH @ 50PA Their This Old House
house is over 7 times leakier than that.

< http://www.greenbuildingadvisor.com/blogs/dept/musings/blower-door-basics
>

> I begin to wonder whether cooking and heating with
> gas would even be safe or whether the build up of CO
> and depletion of oxygen might become a problem.

First, heating is not an issue, because furnaces and boilers
are vented. However, as a designer of very energy efficient
houses (have been doing it since 1975) I strongly recommend
against my design clients cooking with gas. Venting poisonous
carbon monoxide into your breathing air is simply unhealthy, in
any house, tight or leaky. You do not want to be breathing
known poisons. Tight houses can still have wood stoves, and
they do not even need to have direct fresh air vents, because
they vent out. What causes problems is kitchen power vents,
that can pull air down woodstove, or furnace flues. So, you
need a system to vent in, as the kitchen vent move air out.
An "HRV" can do that.

New homes in many jurisdictions are now required
to have an HRV. That is a "Heat Recovery Ventilator"
HRVs move air out of the house, and move in fresh
air, while exchanging heat between the two. In Winter
heat is exchanged from the outgoing air, to the incoming
air. In Summer, heat is exchanged from the incoming
air, to the outgoing air. There are also ERVs. "Energy
Recovery Ventilators" which also exchange humidity.
ERVs are primarily used in the South. HRVs assure
that adequate fresh air is distributed throughout the
house, and that tight houses do not get too humid
during the Winter. Expect them to be required
by all building codes, fairly soon.

> A local family was very nearly killed a few years
> ago when a forced draft furnace created enough
> back draft to fill the house with smoke and co
> from the smoldering embers in a fireplace, and
> a gas fired water heater.

Many energy efficient houses do not have any gas
or other combustion fuels coming into them, except
maybe a wood burner, which has its own provision
for venting, whether direct, or indirect. With heating
loads reduced to near zero, there is no reason to
use gas instead of electricity. Many actually use
electric resistance heating, though there are now
some very inexpensive, and also highly efficient
heat pumps available. Heat Pump Water Heaters,
are also being used. Highly energy efficient houses
are quite different from what we grew up with, and
sometimes when someone tries to do things, just
halfway, they produce clashes, that can be
dangerous.

Posted by: "Aki" 01dyna@gmail.com

> There's a drive, to save energy (heating and cooling costs),
> to make homes as airtight as possible. I think that's a very
> BAD thing.

Hello;

Respectfully, I suspect that is probably because you lack
knowledge on the subject, and are imagining things that
simply are not true. The truth is that the "BAD" is in the
halfway efforts, that are now standard practice. Older
homes, that had no insulation in the walls, and used
huge amounts of fuel to warm them, had pretty clean
air, because they were extremely leaky, even inside
of their walls. Highly energy efficient houses, built
properly, are also healthy, because they are designed
to bring in fresh air, and to keep moisture out of their
walls. We are designing and building houses better
than ever before, but that does not mean that some
mistakes do not still get made along the way, by
some builders and designers. But, so far, at no time
in history, has anyone built a perfect house. We are
still trying, and doing better than ever.

> There needs to be some source of fresh air to keep us
> from rebreathing the same, stale air over and over.

Tight houses have HRVs, and tests show that the air in them
is magnitudes cleaner than the air in most leaky unvented houses.
Leaks are a terrible way to vent a house, because leaks lead
to depositing moisture inside of the walls, which feeds growth
of rot, mold and mildew, which is even more unhealthy than
the pollutants that otherwise would be in the house. Houses
need to be vented through a controlled system, not through
the structure.

> I would think that developing an air circulation system that
> would introduce fresh air, maybe by forcing it through the
> heating/cooling system first would enable homes remain
> super efficient yet keep the air quality at optimum levels.

You are correct, but decades behind the times. In many
jurisdictions, such as Nova Scotia, where I recently designed
one of my very energy efficient, Solar houses, the building
code requires ALL houses to be tightly built, and to have
an HRV.

-Laren Corie-
Natural Solar Building Design and
Solar Heating/Natural Cooling/Energy
Efficiency Consultation Since 1975
www.ThermalAttic.com (many new
photos and pages, coming soon)

Read my Solar house design articles in:
-Energy Self-Sufficiency Newsletter-
www.essnmag.com

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http://groups.yahoo.com/group/LittleHouses/

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