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Home Comfort tips.

Low relative humidity is an indicator of excessive heat-loss

Low indoor humidity during cold Montreal winter days is a tell-tale sign that large amounts of heat is escaping from the house. Building codes before Y2K allowed for small openings in the building envelope allowing cold outside air to infiltrate and warm inside air to escape. This normally results in lower relative humidity levels inside the house. A negative side effect is that it creates irritants to its occupants such as, dry skin, nose bleeds, dry eye, static electricity, etc.

The ideal relative indoor humidity is 40-50 %.

Building codes have changed over time and with it improved insulation and standards for air tightness of the building envelop. The biggest improvement was phased-in at Y2K when the with the introduction of a new R2000 National building code. This standard has greatly improved insulation and air tightness of buildings. A home constructed to this standard does not necessarily have to conform if not tested and independently verified. Sometimes home improvements after construction can also compromise the energy efficiency integrity.

Fig.1  Common sources of heat-loss in a detached home.

Static electricity, dry skin and cold air draft problems.

Skin irritation problems, nose bleeds, dry eye, ect. are often caused by low relative humidity of the indoor air.

A home with low relative humidity :

For a poorly insulated house when the outdoor temperature drops the indoor humidity drops also. The most common quick band-aid solution used to reduce this irritant is to install a central humidifier to the furnace or to add one or several room humidifiers around the house. This solution partially alleviates,  but does not solve the under laying problems at hand.

           The humidity level in older homes can be raised to normal levels without                          the help of external humidifiers.

A home with air infiltration and attic venting problems can produce a costly chain of events.

1. When the outdoor temperature drops  the chimney effectcomes into play. Cold outside air is drawn into the house. The colder it gets the worst the problem gets.

2. The cold humid outside air warms-up rapidly when it enters the house. The air volume increases rapidly and the relative humidity drops.

3. The expanded warm air rises to the upper floor and like a balloon under pressure it will find any small opening in the ceiling and vapor barrier to escape into the attic where the warm air condenses into a water vapor.

4. If the attic is poorly vented the warmer air is trapped and causing the snow on the roof to melt in affected areas and turn accumulated snow into ice. This can cause ice damming to occur on the roof.

5. This in turn can roof shingles in the effected areas to rot prematurely and create roof leaks when left unchecked. Ultimately it means pre-mature replacement of roof shingles that normally could last 20-25 years forcing the home owner to prematurely spend thousand of dollars on roofing repair or placement work


Is your home effected ?

This problem is widespread and under-estimated, especially in homes build before 1990. The older the house, the more air infiltration problems can expected and the worse the problem can be. A quick way to find out if your house is effected is to verify during the February – March time-frame if any ice built-up has occurred on the lower parts of the roof and around dormers. During summer months the advanced effects of this problem can also be noticed easily. Roof shingles generally deteriorate at the same pace across the roof over time. When in areas usually around lower roof and dormers the shingles appear to have deteriorated more than on other parts of the roof it is often an indicator of underlying problems.


Ant problems.

Another unwelcome side effect of poor insulation and excessive air leakage into the attic can be an ant infestation in the attic. Ants love humidity. Generally ant problems in the house are caused by persistent pipe or faucet leaks. A humid attic or minor roof leaks can also be the cause of a lingering ant problem.


Residual heat.

Home electric power needs have changed dramatically over the last 50 years. A standard family home constructed during 1950-60 came with a 60A power distribution panel. As more convenience and entertainment appliances came to market the standard panel capacity almost doubled to 100A after 1965. To satisfy the energy needs for an ever increasing amount of appliances, convenience and electronic entertainment gadgets ever more electric power is required in a home. Today standard family seize homes are equipped with 200 and even 300A power distribution panels.

Most of the added electric power capacity is used to power multiple TV’s, computers, fridge, freezer, hot water heater, recessed lighting etc. Some devices consume power even when powered OFF. On average 60-80 % of this electricity is converted into heat and released into the house. This residual or indirect heat can help to keep the house warm during winter. During spring summer and autumn this residual heat can make the house to warm and uncomfortable, creating the need for air conditioning.



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