Another hot muggy dusty summer is just around the corner. The grass is growing, the trees are budding and the pollen is flying. Summer time in Ottawa is a beautiful season to enjoy outdoor fun with healthy activities. Indoors conditions are not always so carefree. Typically warm summer temperatures are the perfect opportunity to naturally ventilate our indoor environment. Open doors and windows dilute wintertime dust mites and bio effluent accumulation from carpets and findings. Get a healthy dose of fresh air. Yes, yes, yes all the things are generally good for indoor air quality; however, take a moment to reflect what may happen during this summertime ventilation exuberance.

Pollen- Dust and Allergies

Consider the allergy sufferer possibly sharing your living space. At peak pollen season is it wise to open windows (screens stop bugs not pollen & dust) or should we air condition and filter the air with a good quality H.E.P.A furnace filter?

Air can be contaminated by a range of very different particles such as dust, pollen, soot, smoke, and mold spores. Many of them can harm our health, especially very small particles that can enter deep into the lungs. What is known about the different health effects of particles?”

Respirable suspended particulates (R.S.P.) can be common house dust, mold spores, pollen or construction dust. To the allergy sufferer an irritating RSP condition may affect them indoors or outside the house. It is impossible to control outdoor (ambient) dust conditions; however it is completely possible to reduce dust in a controlled, air filtered, dryer indoor environment.

”The aerodynamic properties of particles determine how they are transported in air and how they can be removed from it. These properties also govern how far they get into the air passages of the respiratory system. Additionally, they provide information on the chemical and the sources of particles.”

”The sampling and description of particles is based on aerodynamic diameter, which is usually simply referred to as “particle size”. Particles having the same aerodynamic diameter may have different dimensions and shapes.”

”Based on size, particulate matter is divided into different groups: The coarse fraction contains the large particles with a size ranging from 2.5 to 10 µm (PM10 – PM2.5). The fine fraction contains the smaller ones with a size up to 2.5 µm (PM2.5). The particles in the fine fraction which are smaller than 0.1 µm are called ultrafine particles.” One micrometer is equal to one, one millionth of a meter. The average human hair is 80 microns in diameter. Mold spores on dust mite fecal matter is typically 2.5 to 5 microns.

Modern HEPA filters (High Efficiency Particulates Arrestor) filters to your existing furnace (move the furnace fan control from auto to on) reduce airborne particle and reduce household R.S.P. Low voltage electrostatic furnace filters can be flitted to most furnace and cost between $115.00 to $350.00 dollars. The installation of these types of filters can be simple as;

1. Determine the size of your filter by pulling it out of your furnace (turn off the furnace first).
2. Pick-up the same size M.E.R.V. 17-20 or H.E.P.A. low voltage ELECTROTATIC filter from your local hardware store.
3. Slide the new filter into your furnace filter housing say 1”x16”x24”.
4. Plug the low voltage adaptor into the wall outlet or read the instructions and connect the 3 x colour coded wires to your low voltage terminal on the furnace (usually where the thermostat wires hook up to the furnace).
5. Turn the furnace on and move the switch on the thermostat from auto to on for continuous fan operation.

Basement – Moisture Control

If we rely on natural ventilation all summer long, how do we control lower basement level humidity? Hot muggy summer weather conditions generate moisture on cool indoor surfaces. Cooler surface in mid July are generally found on basement floors and wall assemblies.

The summer ambient relative humidity levels are very high. To explain this moist warm air/cool surface condensation condition we can Google a Psychometric Calculator and plot our relevant conditions. Sounds pretty boring eh? Or better yet, we can think of a cool frosty beer just fresh from our fridge. The moment the cool beer bottle is placed on the picnic table it begins to sweat or moisture begins to condense on the beer bottle surface. The beer in the fridge was in a dry cool environment. The same beer on my patio is in a warm- high RH environment. When the warm moist air touches the cool bottle surface the drop in the bottle surface temperature condenses the moistures because cool temperatures hold less moisture than warm temperatures.

If my fridge temperature is set at 1˚c and the exterior humidex is 85% the beer will condense moisture as soon as it is exposed to the outdoor air.

Now while I enjoy my beer on my rear deck I realize my basement windows are open because I think I am getting rid of the “musty basement smell”. No, no, no, if the previously mentioned outdoor relative humidity is 85 % and this warm afternoon picnic temperature reaches 32°c (common Ottawa conditions) then I am creating condensation on all my cool basement floor and wall cavity surfaces that are 30˚c or cooler. Just as the cool beer bottle condenses moisture on the cool glass surface. Most basement slab surfaces I’ve tested don’t get warmer then 25˚c in mid summer.

We must consider everything that is organic (wood, paper, cotton, carpets with skin cells and dander in them) that comes in contact with this condensed moisture provides an ideal environment for mold growth which contributes to my “musty basement smell”.

During peak pollen, high humidity /temperature days it may be better to close your windows, turn on your air conditioner, filter the air and dry out your basement instead of opening your lower level windows.

Rising electricity costs make this option less desirable. More efficient air conditioning with a high SEER rating can reduce these unforeseen expenses (SEER- Seasonal Energy Efficiency Ratio). Another option is to install a 50 pint Energy guide (Enerstar) rated dehumidifier to control basement humidity during summer-peak hot/humidity periods. Ventilation is still a great way to improve indoor air quality however; understanding the best time to naturally ventilate may limit your home indoor air quality concerns. Knowing when to reduce lower level ventilation may control unnecessary moisture accumulation in your basement.

So remember a frosty beer on your patio is good. A sweaty basement wall and floor assembly is bad.

Have a Healthy summer.

Cheers.

Shawn Rankin