Make up air
Last Post 05 Jan 2008 07:04 PM by trigem1. 8 Replies.
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dgravlinUser is Offline
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27 Nov 2007 09:04 PM
Eliminating infiltration was one of the main reasons I built with SIPs.  In California, all one has to do it look at your title 24 report to see that infiltration is usually the largest cause of a building's energy load.

So, in addition to using SIPs, I am employing spray foam to seal rim joists and any other non-SIP part of the house (the roof & walls are SIPs) and any joints that might leak air.  I'm also taping (SIP tape) all spline joints on the interior face of the SIPs.

That said, I will soon be introducing several conduits to outside air - kitchen ventilation fan, bathroom fans, and a clothes dryer.  All of these will be fitted with backflow prevention devices to minimize the infiltration of air.  However, when they are in operation, they will be sucking a significant amount of air out of the house.  A clothes dryer running for an hour can suck 7500 CF out of a house.  The kitchen ventilation hood can do even more than that.

I don't have a fireplace inside the house (there are a couple outside fireplaces) so I am not concerned about the problems that they can cause when the house is de-pressurized.  However, I still am wondering where the replacement air will come from when the kitchen ventilation fan and clothes dryer are running - sending over 500 CFM out of the house.

Anyone have any thoughts or experience with this issue?  ERVs do not really solve this since they only exchange air - they don't balance it.  Will residential make up air systems be necessary some day?

Dave
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27 Nov 2007 11:27 PM
imploding SIP houses? The whole idea of a fresh air exchanger is to put a controlled whole in the seal. The control part is that the air from the outside passes across a radiator so that the inside temp is used to exchange the incoming temp with the outgoing temp prior to allowing the outside air past the seal. Pressure is created by the HVAC system which always creates positive pressure into the rooms and negative pressure back to the system. One of the room vents pushes air outside the seal. The incoming air is sucked into the HVAC system after conditioned to the room temp. The HVAC isn't necessary however. Have you ever used a radiant heater in an rv or tent? You simply have to have a crack in the window for 02 to move from high concentration to low.
cmkavalaUser is Offline
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28 Nov 2007 03:55 PM
Dave;

I have seen at the IBS ERV's that are capable of pressurizing the house (can't recall who made them)
The Florida solar energy center has reccomended to us that in lieu of a ERV a simple 4" duct ( with damper) from the outside to the return air side of HVAC unit will help to pressurize, however being unconitioned it is also adding to the load. The damper helps to balance
Chris Kavala
info@southernsips dot com
1-877-321-SIPS
FL. Lic # CBC036455, GA Lic. RLCO000624, LA Lic. # CL33845
nailpounderUser is Offline
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28 Nov 2007 08:15 PM
Dave

Have your HVAC person install a motorized damper from an outside air source to the return side of the air handler. You can control this manually or he can tie it into all the fan circuits so it only opens when a fan comes on. This can be done with low voltgage wiring and contactors. Also you might think about installing the outside air source in a buried pipe so the ground temp can condition the air some what.
John in the OCUser is Offline
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04 Jan 2008 08:22 PM
We are just starting our first SIP home.

I am a bit confused about fireplaces.. Do I understand that HRV systems can create a negative pressure therefore makeup air must be independantly provided?

Any systems exist to correct or do any manufacturers make as fireplace configured for tight (SIP) houses?
cmkavalaUser is Offline
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04 Jan 2008 08:37 PM
Posted By John in the OC on 01/04/2008 8:22 PM
We are just starting our first SIP home.

I am a bit confused about fireplaces.. Do I understand that HRV systems can create a negative pressure therefore makeup air must be independantly provided?

Any systems exist to correct or do any manufacturers make as fireplace configured for tight (SIP) houses?
John;

A HRV or ERV should not cause negative pressure, I have a fireplace (majestic) in my SIPs house, but the exterior air supply is not sufficient due to the tightness of the house.
And simply turning on a bath exhaust fan, clothes dryer, kitchen exhaust fan or running air handler will cause negative pressure and make the fireplace  smoke if glass doors are left open .
In my next home I plan on installing an EPA fireplace that will depend on exterior air only for combustion. Ther are many out there here is one:

http://www.icc-rsf.com/en/fireplaces/foyer_opel.asp#


Chris Kavala
info@southernsips dot com
1-877-321-SIPS
FL. Lic # CBC036455, GA Lic. RLCO000624, LA Lic. # CL33845
PanelCraftersUser is Offline
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05 Jan 2008 02:15 PM
Posted By cmkavala on 01/04/2008 8:37 PM
In my next home I plan on installing an EPA fireplace that will depend on exterior air only for combustion. Ther are many out there here is one:

http://www.icc-rsf.com/en/fireplaces/foyer_opel.asp#



Now, if someone would create a sealed combusion true Direct Vent wood burning appliance, I would be happy. So far, all that I've found is a Direct Vent pellet stove.
....jc
If you're not building with OSB SIPS(or ICF's), why are you building?
John in the OCUser is Offline
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05 Jan 2008 03:08 PM
Indoor air quality has not reached a true science yet has it? Especially when it comes to fireplaces with duel fuel in newer tight (SIP) homes.....

The HRV companies are quick to distance themselves from being a make up air supply to overt negative pressure and interior smoke... has anyone found a true system with science behind it for SIP wall homes and dual fuel fireplaces?
trigem1User is Offline
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05 Jan 2008 07:04 PM
John,

What I did in my SIP house is to install a Fireplace Xtrordinair that I placed the blower intake on the outside of my house to bring fresh air in through the heat exchanger above the fireplace. This brings in fresh heated air into the house, slightly pressurizing the house and making sure there are no back-drafts down the chimney. I still need to be careful that all exhaust blowers are off while I start the fire until it warms up enough to start the blower.

Steve Etten
SteveEtten@GrandCountySIPs.com
www.GrandCountySIPs.com
Steve Etten
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