Ventless Crawl With Vacuum

[Brian A. MacNeish]

Originally Posted by tfarmer

Yes, It comes up through the crawl next to the furnace which is the firewall area (but up through the ground) No switches were noted in the area of the vacuum, no thermostat was noted (outside temp was 26 degrees and snow)
Continual sucking was noted

Was there a ground cover of plastic to act as a moisture barrier for evaporation from the soil?

If not, this may be there to suck moist air out of the crawl space. Not a very good approach to controlling /dealing with ground moisture evaporation. Along the lines of the Humidex idea for summer humidity in full and partial depth foundations.

[Troy Farmer]

Another pic to add to the whole thing.

This just dawned on me, this pic is a return in the west hallway on the wall close to the floor. See how it terminates in the crawl (I'm assuming what would you guys think?)

[Troy Farmer]

Vapor barrier is good throughout.

Just a note: Temp in the crawl was a nice 64 degrees with a RH of 36%

[Michael Larson]

So they are drawing conditioned air from inside the house and venting it outside through the inline fan motor?

Now I am confused.

[Troy Farmer]

Me to, I have put a call into the builder but have heard nothing yet

[Brian A. MacNeish]

Originally Posted by mlarson

So they are drawing conditioned air from inside the house and venting it outside through the inline fan motor?

Now I am confused.

The Humidex is also now being promoted as an air exchanger as well as a basement dehumidifier. The "dehumidifier" function was the first intended use. Had a few "discussions" with the inventor, Mark Lestage, a refrigeration technician with a bit of history in residential air exchangers.

Gave you folks the American dealer website before. Here's the Canadian homepage:

http://www.humidex.ca/

[Troy Farmer]

Just got off the phone with the builder.

He doesn't know the name of the exact system (typical builder)
the reason for the unit its the most energy efficient to use, it saves on insulation (you only have to put it on the foundation walls not under the floor) Lower heat bill, he also adds the floor stays warmer that would explain the warmer crawl space 64 degrees. He said, in his own home the tile stays so much warmer. It costs about $250 for the HVAC guy to install and its speed is 20cubic feet per min (no bad) It takes the inside air of the house and puts it into the crawl space then spits it out a the other end.
Pretty cool system.

[Brian A. MacNeish]

Originally Posted by mlarson

Troy, I have also seen this type of unit used for clothes dryer venting on long runs.

http://www.fantech.net/dryer_boosting.htm

[Troy Farmer]

I was looking at the site earlier and also noticed that they do radon mitigation units as well pretty cool stuff.

[Brian A. MacNeish]

Originally Posted by tfarmer

Just got off the phone with the builder.

He doesn't know the name of the exact system (typical builder)
the reason for the unit its the most energy efficient to use, it saves on insulation (you only have to put it on the foundation walls not under the floor) Lower heat bill, he also adds the floor stays warmer that would explain the warmer crawl space 64 degrees. He said, in his own home the tile stays so much warmer. It costs about $250 for the HVAC guy to install and its speed is 20cubic feet per min (no bad) It takes the inside air of the house and puts it into the crawl space then spits it out a the other end.
Pretty cool system.

Unless they damped it down and measured the flows, I'd say it's moving/exhausting more air and heat than builder says since the fan isn't seeing much static pressure!!

See: http://www.fantech.net/inline_duct.htm

(1) The system is giving a continual exhaust-only general ventilation/air exchange for the house but with no heat recovery

(2) Does the house have naturally vented heating applainces in the area of the exhaust end of the duct? and does it these areas of the home under negative pressures that might at times back draft an appliance?

Not a system I would put in my home. In the long run, I'd take the insulation under the floors......cheaper and done well......no maintenance or replacement or electricity use.

[Brian A. MacNeish]

Originally Posted by tfarmer

I was looking at the site earlier and also noticed that they do radon mitigation units as well pretty cool stuff.

Just a note: Fantech bought out an HRV manufacturer in Buctouche, New Brunswick where the gent that invented the Humidex used to take care of the UL or CSA testing of prototype units for electrical certification.
The 2 Maritime Provinces of New Brunswick and Nova Scotia, with a total population of about 1.75 million, have 4 major home ventilation manufacturers (3 have well developed HRV lines).

[Troy Farmer]

Originally Posted by Brian A. MacNeish

Unless they damped it down and measured the flows, I'd say it's moving/exhausting more air and heat than builder says since the fan isn't seeing much static pressure!!

See: http://www.fantech.net/inline_duct.htm

(1) The system is giving a continual exhaust-only general ventilation/air exchange for the house but with no heat recovery

(2) Does the house have naturally vented heating applainces in the area of the exhaust end of the duct? and does it these areas of the home under negative pressures that might at times back draft an appliance?

Not a system I would put in my home. In the long run, I'd take the insulation under the floors......cheaper and done well......no maintenance or replacement or electricity use.

(1) yes

(2) Not in the area of the exhaust. Dint Know the other

[David A. Andersen]

This application appears to be a design for a serious moisture problem. I see no reason for the fan. It is an energy hog.

To condition the crawl, the HVAC return can be piped to the outdoors (this stops unconditioned air infiltrating the house and conditions air before use). All crawlspace openings closed (no vent needed as air exfiltration will occur at a sufficient rate from normal construction leakage). A controlled (balanced) HAVC air supply to the crawl to provide a specific positive pressure.

Outdoor air is treated in heating and cooling before entering the house.
A positive air pressure rather than a negative in the crawl. Less chance of contamination. No moisture infiltration during summer humid weather.
Also acts as a positive pressurization Radon Mitigation System.
HVAC system controls moisture in summer.
Blower motor is not needed, or costly to operate. HVAC blower is operating anyway.

A blowing system has more positive issues than a sucking system.

[Brian A. MacNeish]

Originally Posted by dandersen

This application appears to be a design for a serious moisture problem. I see no reason for the fan. It is an energy hog.
Agree......but if the house is tight enough to need continual (or a fair amount of intermittent) ventilation might not be that bad. If the continual ventilation overdries the house in the winter and they have to use a humidifier, then adjust the sysem flows downward.......but to use it for a warm floor.....crazy.


To condition the crawl, the HVAC return can be piped to the outdoors (this stops unconditioned air infiltrating the house and conditions air before use). All crawlspace openings closed (no vent needed as air exfiltration will occur at a sufficient rate from normal construction leakage). A controlled (balanced) HAVC air supply to the crawl to provide a specific positive pressure.

Outdoor air is treated in heating and cooling before entering the house.
A positive air pressure rather than a negative in the crawl. Less chance of contamination. No moisture infiltration during summer humid weather.
Also acts as a positive pressurization Radon Mitigation System.
HVAC system controls moisture in summer.
Blower motor is not needed, or costly to operate. HVAC blower is operating anyway.

A blowing system has more positive issues than a sucking system.

Possibly if the air in the house being blown outward during cold weather is fairly dry. If it contains quite a bit of humidity (from a humidifier especially),it can cause condensation problems in walls and attics. I have seen a north facing roof system rot out over 20 years or so from a furnace mounted humidifier not being properly controlled. It was next door to my ex-partner's place.