Positive pressurized attic space for fire protection and summer cooling?
I have a 4 year old Deltec home in Central Washington State. Zone 5B. Deltec homes are essentially round houses that have a center cupola that is vented. (Deltec homes has a web site if you need photos) This house has 2 wings that were stick built on site. The wings have continuous soffit vents and continuous ridge vents. The ceilings between the conditioned space and the attic were meticulously sealed. I am attaching a photo of the cupola from Deltec’s web site showing the vents.
This portion of Washington has huge wildfires. Just this year, the city I live in, (Wenatchee) lost 24 homes and 4 commercial buildings in one fire. All of those buildings were ignited by burning embers. Every year that we have been here we have had large fires within 5 miles. Some within 3/4 of a mile. The house has a class 1 roof and fiber cement siding. The area around the house is Firewise landscaped and has exterior sprinklers. Everything is designed to protect from wildfires except for the attic ventilation.
Burning embers entering the attic is a known method of ignition. Testing done at the Insurance Institute for Business and Home Safety shows burnig embers entering attic vents with 1/8 inch screens. There is a fascinating video on You Tube “IBHS Research Center Ember Storm Test Highlights” https://youtu.be/IvbNOPSYysshttps://youtu.be/IvbNOPSYyss
The house is well protected with the exception of attic vents. My questions are centered around creating a positive pressurize attic by building a dedicated air intake that would draw air through a yet to be designed filter. The filter would need to filter out burning embers.
I was wondering — we buried a large portion of the intake pipe to take advantage of lower ground temperatures. Summer temperatures here are routinely in triple digits. There is also an underground 10,000 gallon water tank that we might want to use as an air intake, drawing the air from the space above the water. We would need to do some testing but I think embers would have a difficult time making it through the water collection system into the tank.
I understand that some of this is really out there, but I can’t see another way to protect the attic space short of trying to cover every vent. That would take hours (that we might not have) and isn’t going to happen if I’m away from the house. My thoughts are that the system should be running most of the time in fire weather, as opposed to having to switch it on as a fire approached.
What do you think? Thanks for your input.