fresh air for the house

[jeff_gates]

We are building a 3 story 2500 sq foot in the Seattle area and are doing a radiant floor system for heat.

Any ideas on what equipment to use to bring in fresh air? Most units want to tie into a forced air system. Also we don't want to dump cold air into the house so a air exchange would be nice. To top it off the wife doesn't want holes all through out the house.

Thanks,
Jeff

 

[mrpizza]

Re: freash air for the house

Are you doing central air? If so, you are looking for a product called an ERV (Energy Recovery Ventilator.) They do tie into your hvac system and exchange the heat or cool inside with the air coming in, and filter it.

If Not doing central air, I dont know.

 

[jeff_gates]

That's the problem, we are not doing forced/central air.

 

[mrpizza]

In that case, there are ERVs that work standalone, but they do require some small ductwork and vents throughout.

 

[BillK]

If it's that nice out there that you don't need AC, how about just opening a window or two ? Or is that too old fashioned ?

 

[jeff_gates]

The wife wants to make sure that we are balanced.

6 exhaust fans at 110 CFM each for 660CFM
1 kitchen hood about 1000 CFM

of course these are not running all the time
will the HRV or ERV be able to handle the air movement?
We are going to run some duct work in the walls but not much.

 

[yeldogt]

What's the humidity throughout the year ?

For the stove hood ....I use a system from CCB innovations for make up air -- in my new build it will open a damper connected to a 10 inch duct to the outside .. my other place is an 8". You can duct it back to an area of the house where the air will be mixed .. normally high in the building. It can also be split -- say into two 6" returns. In my case we use the supply ducts of the HVAC to dump the outside air.

Even with spray foam -- a bathroom vent running will have no problem finding 110 cfm's. They will not run all at once.

My house in the country uses an ultra air dehumidifier -- the inlet to the unit has an 8" for internal air and 6" for outside air. The 6" has a damper. The unit will cycle for both humidity and outside air to make sure the house get 3-4 refreshes day when we are there. We "T" it off of the same inlet duct for the makeup air.

You can also do a small -- HRV or ERV -- I like the low CFM's running all the time vs the high powdered running in cycles. I'm also in a Radon area .. so setting them for a bit of positive house pressure is what I like. This can also be a "T" of the large inlet vent for the "makeup" air

Most times balanced is not what you want .. having a bit positive is better.

 

[jbwilkins]

For the Kitchen Hood you'll have to include a make up air to meet code.....Anything over 300 CFM's typically require it...

There are 'smart' exhaust fans that can be purchased. They interconnect and work together to meet the ASHRAE Standard 62.2....Typically leakage will work for the exhaust fans...There are also switches that can control fans..(I believe Honeywell makes one)....The other option is to just put a fan on a timer (say in the laundry)....

If you go the exhaust fan route look for something with no more than 1 sones (it's a sound level rating)......You don't want to be hearing the thing run in the middle of the night when you're trying to sleep....

 

[jeff_gates]

These are all good ideas, I think we are going to use a combination of motorized and pressure sensor to bring in fresh air, plus one of the bathroom fans will be constant on to draw fresh air into the house.

 

[yeldogt]

Pressure sensor?

Many bathroom fans -- CFM too high.. and you don't want negative pressure. Keep the bathrooms fans for what they do the best == Fantech makes a great external unit.

Do you need dehumidification?

 

[Vermaraj]

We have two of dx200:
http://www.ultimateair.com

Since they run continuously they are piped in place of the exhaust fans. The return air goes to the bedrooms. Pretty unobtrusive 4" exhaust and supply ducts. The manual has schematic for stand alone ducting.

It use two ECM fans to maintain positive pressure in the house. If the big kitchen hood kicks in it will trigger ERV to shutdown exhaust side. Automatically providing makeup air.

Also have the coils to temper air. Pretty useless for cooling, but do a great job of tempering air in the dead of winter. Under 20 deg F ERV needs help to avoid cool draft. Under 0 deg F electric preheat kicks in.

Makes a world of difference. When the system is shut off for a day you notice it in the bathrooms and kitchen.

 

[yeldogt]

We have two of dx200:
http://www.ultimateair.com

Since they run continuously they are piped in place of the exhaust fans. The return air goes to the bedrooms. Pretty unobtrusive 4" exhaust and supply ducts. The manual has schematic for stand alone ducting.

It use two ECM fans to maintain positive pressure in the house. If the big kitchen hood kicks in it will trigger ERV to shutdown exhaust side. Automatically providing makeup air.

Also have the coils to temper air. Pretty useless for cooling, but do a great job of tempering air in the dead of winter. Under 20 deg F ERV needs help to avoid cool draft. Under 0 deg F electric preheat kicks in.

Makes a world of difference. When the system is shut off for a day you notice it in the bathrooms and kitchen.

You find it's enough for the bathrooms? does it have a boost function? I found it was not enough and was glad to have also included dedicated exhaust fans . The fresh air system was pulling from two bathrooms and a powder room -- at 100cfm it was not enough. Worked great for bringing in fresh air --

I also need some dehumidification.

yours must be moving a lot more air -- my kitchen hood needs 1200cfm on high. for the small amount of time it runs at full speed I pipe it into the hvac -- if you have a VS system they are running most of the time so tempering is rarely need.

 

[DC73]

will the HRV or ERV be able to handle the air movement?

Yes if properly designed and installed. If you are in a humid area, choose the ERV instead of an HRV.

DC

 

[PT Doc]

We went with an ERV and had to have makeup air ducting for 1500 cfm kitchen hood. The ERV is Honeywell and I think that it is likely made by Aprilaire. Quite a bit of ducting that was done during the home build so that the ducts could be sealed to the house with gaskets and Tyvek etc. We are happy with setup. No exactly cheap but my wife and I worth it.

 

[Vermaraj]

You find it's enough for the bathrooms? does it have a boost function? I found it was not enough and was glad to have also included dedicated exhaust fans . The fresh air system was pulling from two bathrooms and a powder room -- at 100cfm it was not enough. Worked great for bringing in fresh air --

I also need some dehumidification.

yours must be moving a lot more air -- my kitchen hood needs 1200cfm on high. for the small amount of time it runs at full speed I pipe it into the hvac -- if you have a VS system they are running most of the time so tempering is rarely need.

In the kids bathrooms ~70 sqft ERV is sufficient. The room will have some steam for about 5 mins before ERV clears it completely. I never connected the boost feature. That might help.

IN the mbath I added a 150 cfm Panasonic whisper quiet (highly recommended) because we have a steam shower. We rarely use the supplemental fan (or the steam shower) due to the size of the room.

One draw back of constant ERV circulation s the very low humidity in the house, with the exception of the summer months. In the winter the humidity can get down to low 40s even high 30s. At that point shower vapor is absorbed so quickly that an exhaust is really not needed,