Constant flow of fresh air indoors ?

[john]

Is there such a product out there that could easily be mounted to a window to send in a constant flow of fresh air?

This would be great for cold areas like here where its not a great energy saver to open the windows when its always 10 degrees in the winter.

Im thinking of a device that filters (hepa filter) the air and warms the temperature of the air to room temperature and then flows it indoors.

I have alot of allergies / chronic headaches and crap like that. If I dont open the windows once every 3 days the stagnant air builds up and I feel like crap again. Once I get fresh air in again I feel much better.

Im not even sure if such a product has even been invented yet? If not, someone might be able to get rich trying.

John

[ransley]

If you have a furnace and ductwork there are air exchangers that pull in fresh air, but maybe you have other issues like mold somewhere.

[John McGaw]

There are quite a few products on the market although I've not seen a portable window-mounted type. But no doubt such a beast does exist somewhere.

[George]

You mean like this:

[Joseph Meehan]

I is not going to save any energy over opening the window.

There have been some heat exchangers that use the inside air that is exhausting to warm the air coming in, but the theoretical best it can do is < 50%. The size and cost are likely to be more than you would like.

[john]

Thanks guys to helping me find out the official name for this. (Heat Recovery Ventilator )

With your help, I googled and found this -

Not sure about the quality and durability of it...but its the only one out there so far.

[Norminn]

Our AC/heat pump has a gismo that can be adjusted to change the amount of fresk, outdoor air taken in. Mebbe your furnace has the same.

[nicksanspam]

I is, in an airtight house, but most US houses naturally leak 10 times more fresh air than needed for health, so HRVs and ERVs are useless.

Nick

[john]

I dont know about that.... regardless of how much fresh air leaks out, if there isnt any coming in....thats much worse. I&#39;d rather have atleast some fresh air circulating throughout.

[Chris Friesen]

Not so. According to the National Research Council they&#39;re typically

70-80% efficient.

The theoretical best it could do is higher than that, of course.

Chris

[nicksanspam]

If air leaks out and none leaks in your house will implode.

Nick

[M Q]

Does anyone know any theory that would prevent an impractically large heat exchanger from being nearly 100% efficient? If so, could you please present it?

[Joseph Meehan]

I would have to believe that it is 70-80% of the theoretical max, which would be 35-40% efficient, which I would guess is about right.

Th>

[Joseph Meehan]

It depends on how you are measuring it.

If you start with 80º interior and 60º exterior the best you can do is to get 70º air coming into the home and 70º air exiting the home. That is at 100% of possible exchange, but it is only 50% efficient overall since the incoming air will be colder than what left, but it will be better than having 60º air coming in.

Now if you have an infinitely large exchanger, and you don&#39;t can&#39;t friction or pumping losses, you could approach, but never reach 100%. It can be 99.99999 (with as many nines as you like) but never 100%

[Wayne Whitney]

In a contra-flow heat exchanger, I believe you can get 100% heat exchange, i.e. the air exiting the house is 60 degrees and the air entering the house is 80 degrees.

Cheers, Wayne

[Joseph Meehan]

[M Q]

What law of physics did you have in mind, top poster?

Maybe you should read up on heat exchangers:

[nicksanspam]

In a counterflow heat exchanger, hot and cold fluids flow in opposite directions. If 100 F greywater flows into one end of a pipe and 60 F fresh water flows into the other end of a tube inside the pipe with equal flow rates C Btu/h-F and heat transfer area A in ft^2 and conductance U Btu/h-F-ft^2, NTU = AU/C, E = NTU/(NTU+1), which can be very close to 1 with large areas and low flow rates, ie close to 100% efficiency, vs 50% max for a parallel flow exchanger with both fluids flowing in the same direction.

We might drip 50 gallons per day (C = 50x8.33/24h = 17 Btu/h-F) into a 1.25"x100&#39; plastic pipe around a 3/4" tube with A = 100Pix3/4/12 = 19.6 ft^2 and U = 10 Btu/h-F-ft^2 and NTU = 19.6x10/17 = 11.5 and E = 11.5/12.5 = 0.92, ie 92% efficiency. With 200&#39; of pipe, E = 96%.

It isn&#39;t, other than some way to make the fluids move, eg gravity for greywater and thermosyphoning for fresh water, in a vertical version.

Nick

[Stormin Mormon]

I&#39;ve not heard of anyone doing this, but how about a flex hose like dryer vent. From the air intake side of the furnace to an outdoor vent, like a dryer vent. Every time the furnace runs, it would draw in some slight ammount of fresh air from the outside. Of course, it would gently pressurize the house so you&#39;d lose some heat that way. But, it would be a convenient way to do it, and it sounds like you&#39;re losing heat using the present sytem of open windows every three days. So, it wouldn&#39;t be a major change in the power bill.

[Speedy Jim]

I have done exactly that. It is some help. Screen the inlet against critters.

Careful to place the intake far from any combustion exhausts or even dryer vent.

Jim