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re: erv selection criteria
18 may 2002
larry brasfield   wrote:

>...leakage (which can include flow through cracks and
>open doors in this discussion) varies with the outside
>temperature, so it cannot be counted upon to provide
>sufficient ventilation...

>the coldest days are when leakage heat losses
>are at their highest, tending to vary with
>the square of inside-outside differential.

the square root.

>the coldest days are also the ones that will make an erv
>useful or not.  days when little air exchange will be driven
>by inside/outside temperature difference are not days when an
>erv will be better than a fan.

it's likely a house will have lots of air leakage on the coldest days.

>a lot of infiltration control is choosing windows and doors carefully
>for leakage. caulking and use of film wrapping are very important too.
>i am not ready to declare any of those particularly labor intensive.

how pompous. you might try talking with people who do this work.
it's akin to trying to make a house watertight, like a submarine.

>> ...maybe a house needs a "shurcliff lung," vs an erv. bill shurcliff
>> proposed attaching a bag to the outside of a house, in principle,
>> with a fan that periodically inflated and deflated the bag with air
>> from the house, thus turning all the cracks and crevices in the house
>> envelope into bidirectional heat exchangers, with latent heat recovery...
>> a simpler variation... would divide the house into two partitions,
>> with a fan between them that periodically reverses. this could be
>> very efficient, done slowly, with lots of heat exchange area.
 
>i think that by the time you get enough of a camel's nose effect from
>incidental cracks and crevices to satisfy code mandated air exchange
>rates, you've lost the infiltration battle, by quite a margin. 

would you care to rephrase that in a way that makes more sense?

>that camel's nose effect is really just an erv with somewhat
>poorer performance.

would you have any evidence for this article of faith? a few numbers?

the fan/partition version might have better performance than any erv,
with less hardware. ornl has done some preliminary experiments.
 
nick




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