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Household Venting Options
By Steve Maxwell
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One of the best things about spring is that you can finally open a few windows and let fresh air waft into room that have been hermetically sealed for the last six months. Canada is a land of climatic extremes, and this translates into one of the greatest needs for household ventilation anywhere on the planet. You can ignore this reality -- for a while -- but eventually mold and rot will appear if your house isn’t breathing freely in some way all year long. Here’s a look at some of the hardware available to help you move stale air out and fresh air in.
In the Attic
There are two reasons why attics need ventilation: to reduce summertime heat buildup, and to vent-off moisture that migrates up from living quarters, settling as frost during winter. The least expensive, most easily retrofitted attic vents are static, rooftop louvres. These come in opaque plastic and metal. Even translucent versions are available that admit some light into the attic. All types fit into a hole cut in your roof sheathing and feature a flange that weaves into the roofing membrane to shed rain. If yours is a shingled roof, be sure to have some new shingles on hand when you install any kind of roof vent. You probably won’t be able to pry all the old shingles off in one piece.
Other styles of attic vents include soffit louvres that fit under the roof overhang, and vent strips that can ventilate the peak on most sloped roofs. These are barely visible, yet particularly effective because they catch the wind, offering fresh air in areas that can’t be ventilated in any other way. Peak vents are also ideal for buildings of historical significance that would be compromised by any other kind of more visible vent.
The rooftop turbine ventilator (often called a whirligig) uses wind to operate a fan that boosts attic air movement, without electricity. An electrically powered cousin of the whirligig -- the roof top fan -- is also available. It moves lots of air, without the prominent stature of the turbine.
In Your Living Quarters
There are many electrical devices that help move stale air out and fresh air in. But wherever you find ventilation air streams moving within ducts that are very different in temperature than their surroundings, there exists the potential for condensation and frost buildup, either on the outside of the duct or within it. Bathroom exhaust fans that push warm, humid air outdoors through a cold attic are one common example. Another occurs when a heat recovery ventilator draws frigid, wintertime air through a duct within a warm area. The solution to the hazards of condensation and frost build up in cases like these is factory-insulated, sealed, flexible ducting. This is a three-part product: a flexible inner duct core; a fiberglass insulating sleeve; and a continuous polyethylene vapour barrier tube sealing the whole thing. Although highly-effective, it’s crucial that the outer poly layer be completely air-sealed where it connects at both ends or passes through exterior walls. If not, warm moist air will enter the insulating layers, causing hidden condensation in most cases. Expanding, spray-applied polyurethane foam and high-quality duct tape are the two best sealing products you have at your disposal.
Confused by all the indoor ventilation appliances available? It’s really not as complicated as it seems. Most fall into one of three categories: room-specific exhaust fans like those found in bathrooms and kitchens; whole-house exhaust systems that draw stale air from several areas at once; and heat recovery ventilators (HRVs) that extract heat from stale indoor air while exhausting it outside and heating an incoming stream of fresh, outdoor air.
Got a cold spot in your house? Electrically-powered duct fans are available to boost air flow within forced air heating ducts that need a little help. You’ll also find models designed to move air between different levels of your house through floor and ceiling-mounted grilles.
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Household Venting Options
By Steve Maxwell
|
|
|
One of the best things about spring is that you can finally open a few windows and let fresh air waft into room that have been hermetically sealed for the last six months. Canada is a land of climatic extremes, and this translates into one of the greatest needs for household ventilation anywhere on the planet. You can ignore this reality -- for a while -- but eventually mold and rot will appear if your house isn’t breathing freely in some way all year long. Here’s a look at some of the hardware available to help you move stale air out and fresh air in.
In the Attic
There are two reasons why attics need ventilation: to reduce summertime heat buildup, and to vent-off moisture that migrates up from living quarters, settling as frost during winter. The least expensive, most easily retrofitted attic vents are static, rooftop louvres. These come in opaque plastic and metal. Even translucent versions are available that admit some light into the attic. All types fit into a hole cut in your roof sheathing and feature a flange that weaves into the roofing membrane to shed rain. If yours is a shingled roof, be sure to have some new shingles on hand when you install any kind of roof vent. You probably won’t be able to pry all the old shingles off in one piece.
Other styles of attic vents include soffit louvres that fit under the roof overhang, and vent strips that can ventilate the peak on most sloped roofs. These are barely visible, yet particularly effective because they catch the wind, offering fresh air in areas that can’t be ventilated in any other way. Peak vents are also ideal for buildings of historical significance that would be compromised by any other kind of more visible vent.
The rooftop turbine ventilator (often called a whirligig) uses wind to operate a fan that boosts attic air movement, without electricity. An electrically powered cousin of the whirligig -- the roof top fan -- is also available. It moves lots of air, without the prominent stature of the turbine.
In Your Living Quarters
There are many electrical devices that help move stale air out and fresh air in. But wherever you find ventilation air streams moving within ducts that are very different in temperature than their surroundings, there exists the potential for condensation and frost buildup, either on the outside of the duct or within it. Bathroom exhaust fans that push warm, humid air outdoors through a cold attic are one common example. Another occurs when a heat recovery ventilator draws frigid, wintertime air through a duct within a warm area. The solution to the hazards of condensation and frost build up in cases like these is factory-insulated, sealed, flexible ducting. This is a three-part product: a flexible inner duct core; a fiberglass insulating sleeve; and a continuous polyethylene vapour barrier tube sealing the whole thing. Although highly-effective, it’s crucial that the outer poly layer be completely air-sealed where it connects at both ends or passes through exterior walls. If not, warm moist air will enter the insulating layers, causing hidden condensation in most cases. Expanding, spray-applied polyurethane foam and high-quality duct tape are the two best sealing products you have at your disposal.
Confused by all the indoor ventilation appliances available? It’s really not as complicated as it seems. Most fall into one of three categories: room-specific exhaust fans like those found in bathrooms and kitchens; whole-house exhaust systems that draw stale air from several areas at once; and heat recovery ventilators (HRVs) that extract heat from stale indoor air while exhausting it outside and heating an incoming stream of fresh, outdoor air.
Got a cold spot in your house? Electrically-powered duct fans are available to boost air flow within forced air heating ducts that need a little help. You’ll also find models designed to move air between different levels of your house through floor and ceiling-mounted grilles. |
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