Air Flow and Ventilation

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TIGHT CONSTRUCTION AND INSULATION

Air Flow and Ventilation

The latest in ventilation techniques and continuous vapor barrier can enhance air quality, and at the same time, reduce excess moister and indoor pollutants in your home

Health and Ventilation

ZERO ENERGY BUILDING ENVELOPE

The latest in ventilation techniques and continuous vapor barrier can enhance air quality, and at the same time, reduce excess moister and indoor pollutants in your home



GOOD TO KNOW

The provision of adequate ventilation in residential buildings can only be assured with a central, whole house, pressure balance, mechanical ventilation system. There is a need to assume a minimum continuous ventilation rate to control the level of indoor air and pollutants generated by occupants or by sources with no fixed or identifiable location. This is accomplished by ensuring a minimum level of makeup air. There is also a need remove some contamination that are generated at fixed locations, such as kitchens and bathrooms. The minimum rate for whole house ventilation, considering mechanical ventilation capacity and natural air leakage, is .35 ACH. Spot ventilation (kitchen and bathrooms) provided on an intermittent basis must be capable of 100 CFM in the kitchen and 5o com in the bathroom.

Require Ventilation options: Heat Recovery ventilation (HRV) or Energy Recover Ventilation, also known as air-to-air heat exchanges or whole house mechanical ventilation system. System balancing is required and an optional incentive is available for the presence of a balancing verification label on the unit.

Tier 2. Minimum apparent sensible effectiveness greater or equal 76% at -13F.

 

The need for make-up air

When exhaust fans operate they pull air from the house-air which needs to be replaced, somehow. In the past, this was done with air that leaked into the building around windows, doors, or foundation cracks. In a well-sealed home, however, there are very few of these leaks. Without an additional source, the fans pull air down chimneys, clues, or other exhaust fans, leading to the entry of dangerous combustion products, or other contamination. The solution is to provide sufficient air to make-up the air that is being exhausted. This is usually done with an insulated duct that enters the house (often in the basement). When properly installed, this dust will only allow the entry of air when needed.


Bathroom Fans

Building code rehires bathrooms have either an operable window or a fan to remove odor and excess moister. A bathroom fan is often quicker and more effective than opening a window – especially during heating or cooling season. In order to minimize moister buildup and mold, it is essential that bathroom fans be installed properly, using short, insulated ducts with no bends or kinks. Additionally, fans must be air sealed at the ceiling and insulated to prevent heat loss into the attic, and ducts must be sealed at all joints and connections, all though to the exit point at the roof or wall. ENERGY STAR rated fans are not only much more efficient, they also are quite and have a longer estimated life.

Many people confuse the ventilation requirements of an attic with those of the living space below. The two types of ventilation are not rated and the systems are completely separate. Attic ventilation is needed to protect the insulation and building materials in the attic from excess moister, caused primarily by air leakage from the moister-laden living space. Although sealing air leaks will reduce the need for attic ventilation (and reduce energy use and ice dam risks), minimum attic ventilation is still required. The ventilation required for the living space, however, is all about providing a safe and healthy environment for the occupants by replacing contaminated air with fresh air.

Ventilation

Point source ventilation is located near the source of the contaminated air, such as in a kitchen, bathroom, or workshop. These are usually exhaust only systems – pulling air from inside the house with fan and exhausting it to the outside through ducts – and are usually controlled by separate, manuals switch.


Exhaust fans

Exhaust fans should be used whenever three are indoor air pollutants (including moister from cooking or showers) that are present in the home. Exhaust fans should be run whenever the pollutants are being introduced into the air and for at least 15 minutes after pollutants have stopped occurring in the home or until signs that pollutants have left the home (for example, when there is no longer any consideration on the windows after a shower). The use of a timer switch to control exhaust fans is a good way to provide adequate ventilation and limit run time.

Exhaust fans need to be vented to the exterior with straight, smooth, short duct runs. Exhaust fan helps to maintain the building’s relative humidity in a range that will tend to minimize moister problem (35% or lower in winter)
Excess humidity can lead to consideration problems and mold growth. Higher quality fans are quiter and more energy efficient.

Recommended Min. air flow in CFM 50
Measured Air flow in CFM 53 CFM

Measure Air Flow in com 49 com
Recommended Min. Air flow in CFM 50 CFM


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