State of Washington Energy Code for new homes—Air Leakage Control and Efficient Ventilation

New Construction is based on a point system. A Small dwelling unit (<1500 square feet of conditioned air space and <300 square feet of fenestration area) needs .5 points; a Medium dwelling unit (>1500 and <5000) requires 1.5 points; and a Large dwelling (>5000) unit 2.5 points.

You can earn points for an efficient building envelope, air leakage control and ventilation, high efficiency HVAC equipment, efficient water heating and renewable energy.

It is a builder’s and or consumer’s choice of what to do to comply with the code.

Remember when I wrote about Air Exchanges per Hour or ACH? This is metric to measure performance for air leakage. You can go to our website to learn more.

You can earn .5 points by reducing the ACH number to 4 and providing whole house ventilation separate from your furnace fan system.

1.0 points can be achieved by reducing the ACH to 2 and providing ventilation via an HRV (a heat recovery unit)—I will talk more about this next week.

1.5 points if you reduce the ACH to 1.5 and provide an HRV.

To achieve a good ACH you must get aggressive on the efficiency of your building envelope. By default your ACH measures will improve when you focus on the building envelope.

We think that the focus should be on building this way. The ACH is a byproduct of sealing the home properly, using more efficient windows and doors and framing the home differently so that you can insulate better. Our ACH numbers consistently range from the high 1’s to mid 2’s.


Please submit questions to Jon can be reached direct at 360.907.5800. Tune into Green Building with Jon Girod on 1550 a.m. on Saturdays at 9 am. See you next week!