Stretch wrote:
...Is it actually available and how much does it cost?
The Smart Vent? It seems to be available, at $365.
Is it cheaper to operate than a dehumidifier
Smart Vent says $8/year. BTW, all this was in my last posting.
and what is the payback period?
Compared to what?
Due to outside RH levels here in Myrtle Beach, SC I duobt that it would be
effective here, but it may work very well in other climates.
They say it works in Florida and Hawaii... NREL's Wilmington NC
weather station has these long-term averages:
Daily min/avg/max humidity ratio deep ground: 63.4 F
Apr 50.5/62.3/74.0 F 0.0080 w
May 59.3/70.1/80.8 0.0114
Jun 67.5/76.5/85.4 0.0147
Jul 71.7/80.1/88.5 0.0168
Aug 71.0/79.4/87.6 0.0167
Sep 65.3/75.3/85.2 0.0142
Oct 53.7/65.3/76.9 0.0099
Smart Vents seem very programmable. They mention 25 different control
algorithms. Ventilating with outdoor air (warmer in winter and cooler in
summer) at times when its humidity ratio is less than the hr of indoor air
seems energy-efficeint, but I suspect that can be improved, in a fairly
airtight house that can store heat and moisture.
In a house like that, with air conditioning, it seems more energy-efficient
to circulate air between the basement floor and the living space than to
exhaust basement air. Surrounded by RH% air, concrete stores about RH/20 %
moisture content by weight, with little dependence on the air temperature.
A 4"x1000ft^2 50K pound basement floor with 8K Btu/F of thermal capacitance
(or more, with no insulation below) can slowly store 500 pints of water as
the RH of the basement air rises from 40 to 60%. The ground below might have
an effective R10 thermal resistance.
If we keep a basement RH 60% all year, the moisture content of the concrete
won't change much. Maybe it's more energy-efficient to easily lower the RH
of the basement air by warming it with dry house air in wintertime to drive
moisture out of the concrete so it can absorb more moisture in summertime.
Nick
From:
To: nick pine
Sent: Monday, June 20, 2005 1:29 PM
We recently received data from an outside, independent year-long
investigation of a Smartvent equipped crawl space. Data was collected
every 4 hours.
Crawl space humidity averaged 46% for the year.
If you would like information about our new HI-IQ ventilator that
pressurizes a home or commercial building with fresh, filtered outdoor
air, let us know. This is the preferred approach throughout most of the
US. In fact, the HI-IQ is the only residential ventilation system that
measures outdoor weather. This product also uses our patented vapor
technology, outperforms ERVs HRVs and at 1/3rd the installed cost.
Used throughout the US, from Florida to Alaska, one Smartvent crawl space
ventilator usually will handle about 1800 sqft. In some cases, special
designs with extra fans are employed. In Hawaii, a 6400sqft crawl space
has additional Smartvent fans and an internal fan as well, all controlled
by one Smartvent main unit. Coastal areas usually need double capacity.
Take a look at the attachment enclosed with this email. It may shed some
light on better ventilation. Few understand the capacity of vapor
pressure based ventilation. Other foundation vents are usually closed by
hand (not sealed), and air will leak through the louvers of all your vents
when the Smartvent runs, rather than just the closest vents.
Virtually all passively ventilated crawl spaces throughout the entire US
exceed 90% RH throughout the summer, so mold and moisture damage are
serious issues.
High humidity in crawl spaces assists growth of molds, spores, and
bacteria. Under a vapor barrier, the humidity is 100%. About the only way
to keep these from migrating into the home is to cut the moisture and
ventilate, slightly depressurizing the crawl space.
Since a crawl space is never cleaned there are dead Ocrittersı, critter
droppings, etc. There may be radon or chemicals in the crawl space.
Gases from all these sources will migrate into the home unless exhausted
to the outside, replaced with fresh air.
On our web site, http://www.smartvent.netcrawlspacevent.htm if you look at
the Crawl Space Moisture Control Study, its chart on page 2, you will see
airborne water vapor is a controlling factor in crawl space humidity.
Measuring only humidity is likely to aggravate a moisture problem. The
original Smartvent that generated the information for the Crawl Space
Moisture Study produced about 90-100 cfm. The new model has been measured
at 295CFM, has upgraded software, and is considerably more effective.
To compare the Smartvent with other systems, the Smartvent is the only
system to compare inside and outside water vapor content. Some other
systems have fans on timers, some operate by measuring crawl space
humidity. Both systems are likely to make crawl space humidity worse.
Installation is fast, installing a foundation vent with clear, outdoor, 35
or 50yr caulk; looks good, cleans up easy. We provide a 6' power cord
that you plug into a 120 volt receptacle in your crawl space. That is all
the wiring you need, no remote mounting required.
Dimensions of the Smartvent are 15 1/4 x 7 7/8 x 8, just slightly smaller
than a concrete block. A Smartvent costs only about $8.00 a year to operate.
You can purchase the Smartvent directly. The Smartvent is $365. We ship
upon receipt of a check, or UPS C.O.D at $8 extra. A two year replacement
warranty is in place. For a C.O.D. shipment, email us the address, and
we likely will ship same day. Note that with a C.O.D. someone must be
there to hand UPS a check.
Larger homes can daisy chain a 2nd (or 3rd, etc.) Smartvent fan-only unit
from the first fan/controller unit. The 2nd unit is $195.
Usually we ship same or next day.
Smartvent, Inc.
3255 Cimarron Drive
Conway, AR 72032
phone 501 329 4915
fax 253 295 9111