Another crawl space plenum

[Joe Hugenroth]

This type of installation was popular here in the 1960's, and there are still quite a few homes with the old system in place. The crawl space was sealed off, with no exterior ventilation, and the A/C and heat were pumped in under the house. Registers were put in holes cut in the floor. I guess they thought by putting plastic on the floor of the crawl, everything would be OK.
Nice system, huh?


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[jwortham1]

Nice system, huh?

That's just.....nasty?

[Charley L. Bottger]

Originally Posted by jhugenroth

This type of installation was popular here in the 1960's, and there are still quite a few homes with the old system in place. The crawl space was sealed off, with no exterior ventilation, and the A/C and heat were pumped in under the house. Registers were put in holes cut in the floor. I guess they thought by putting plastic on the floor of the crawl, everything would be OK.
Nice system, huh?


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Absolutely repulsive???? We use to make fire by rubbing two sticks together but we found there was a better way.

There are just some things that you are not suppose to do.

1. Tug on supermans cape
2. Take a whizz against the wind
3. Shovel crap against the tide
4. A/C system with no distribution piping.
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[Chad J. Willick]

what was the theory for this?

[Charley L. Bottger]

Originally Posted by cwillick1

what was the theory for this?

Static pressure. Put enough static air pressure under a home it has to come out some where.
Its a proven fact that you can only blow so much air into a glass bottle
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[Joe Hugenroth]

Originally Posted by cbottger

Static pressure. Put enough static air pressure under a home it has to come out some where.
Its a proven fact that you can only blow so much air into a glass bottle
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The problem with these installations is that it is difficult or impossible to build up enough static because of the large crawl area. In heat mode, it works quite well only because heat rises. But when the outside temperature is 100 and the A/C is working away, the cold air has a tendency to sink. In a standard A/C blower, there is just not enough CFM to push adequate airflow up into the house.

Besides that, I wouldn't want the air in the house to be blown over sewer pipes and dirt floor in the crawl area.

I have also seen several of these systems retrofitted with ductwork in the crawl space, but no foundation vents were cut in afterwards. Because the A/C system WAS the ventilation, when the air circulation is removed you've got a problem.

[Joe Hugenroth]

Originally Posted by cwillick1

what was the theory for this?

The theory was to save the contractors money.