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Inlet Air requirements according to WA VIAQ


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So my question is regarding the air inlets we see on windows and sometimes with forced air heat systems we see an air inlet duct with damper door and timer here in Washington. Is it just me, or have alot of the builders simply quit installing air inlets?

A few years ago every home had a way to inlet air from the exterior using the trickle ports or the ducts and dampers. But in the last couple years I routinely come across homes that have neither system.

I have heard responses from numerous builders saying that the code was changed and they now allow "Fan only whole house ventilation".

But here is how the exception reads in the code [V303.4.1.5];

Exception: Exhaust only ventilation systems do not require

outdoor air inlets if the home has a ducted forced air

heating system that communicates with all habitable

rooms and the interior doors are undercut to a minimum

of 1/2 inch above the surface of the finish floor covering.

So if you stop here, you can draw a conclusion that no outside air is needed whatsoever....and I think this is what builders, and possibly code compliance officials have done.

But common sense tells me that you are not going to get outside air from a ducted forced air system, unless it leaks like a seive. If it is installed right, then it shouldn't. So I am guessing that the drafters of this code meant that by using the forced air system, air can be inlet through a mechanical damper and duct as follows;

[V303.4.2] Integrated Ventilation System: If a forced air heating

system is installed, fresh air may be ducted into the system

to meet ventilation requirements (see Figure 8-6). An

integrated system consists of:

• A fresh air duct, connected to the furnace return

plenum, sized per VIAQ Table 3-5.

• A damper allowing the proper amount of outside air

to the system.

• A clock timer set to appropriate ventilation periods.

These code references were pulled from the WSU Builders' Field Guide. http://www.energy.wsu.edu/code/

Under the ventilation section;

http://www.energy.wsu.edu/documents/cod ... -2006A.pdf

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