Indoor Air Quality

by | Jul 28, 2020

It’s a dark winter evening. You leave the house and as you emerge outside you feel the cold, fresh air and you pop up, feeling sharp, awake, fresh and lively.

The operative word is ‘fresh.’

Sure, the air is cold and that helps, but in reality we’ve been building sealed buildings since the 80’s with gasketed doors and windows, old drafty houses are becoming fewer. Modern housing is very well air sealed to prevent energy loss. However, the ventilation systems have not been developed and installed at the same pace as the air sealing.

So we need to get fresh air into our houses. We’ve needed more fresh air since the 80’s and as a population we’ve become used to poor air quality.

Yes building code does require ventilation, but often it’s switched and folks don’t hit those switches. We need ‘continuous ventilation’.

The best system is the Heat Recovery Ventilator (HRV). The outgoing ‘dirty’ air is blown out of the house, but before it leaves the heat is stripped out and imparted into the incoming ‘clean’ air. The HRV is always on, and has filters so the air really is clean. HRV’s can be 95% efficient, and in the Lake Stevens house the HRV reduces the maximum building heat load from 14,450Btu/h to 12,800 Btu/h.

The Zhender HRV’s we fit can have Co2 sensors, so they bring in more air when more folks are inside breathing. Also humidity sensors so moist air, the “building-killer,” is automatically removed. Manual boost switches and wireless control are all becoming standard.

The air is still dirty!

Ted Clifton, Co-Owner and Founder of TC Legend Homes, has an air quality monitor in his home. Cooking is a real problem.

The screenshot from Ted’s Footbot monitor shows that it took over an hour for the 200cfm balanced fan to remove the particulates down to the monitor-defined safe level. Ted was cooking hash browns and eggs on a Saturday morning. It is important to note that Ted’s 200cfm fan has a second 200cfm intake fan so it’s a balanced system and can be interpreted as a 400cfm fan.

The lesson is that range hoods are critical to maintaining indoor air quality and should really be sensor-activated. At TC Legend Homes we will be specifying more powerful units; perhaps 800cfm as standard. The presence of particulates indoors is linked to asthma.

The arrival of home automation will easily address this problem and a quick Google search for wireless range hoods yielded plenty of cost-effective models.

The next part of the test is to cook the same hash browns and eggs next Saturday, leave the range hood off, then we’ll see how long it takes a modern super home (Ted lives in the Bellingham Powerhouse) to clear the air with just the HRV.


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