How to Select the Right Ventilation System for Your Home

An air-tight home is an energy-efficient home. The first step toward energy efficiency is to seal any air leaks in your home (the US EPA indicates that 25-40% of heat is lost through leaks in your building shell-imagine how much money you can save on your heating bill) as described in another eHow article. But your home also needs ventilation. Ventilation is described as the exchange of indoor and outdoor air. It's important to address problems with indoor pollutants, moisture and smells. Indoor pollutants include formaldehyde, volatile organic compounds, and radon. When they accumulate in poorly-ventilated homes, they can cause health problems like headaches, drowsiness and respiratory problems. Excessive moisture inside your home can cause mold growth and even structural damage. You also want to avoid uncomfortable drafts associated with uncontrolled or ineffective ventilation systems.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) states that an adequately-ventilated home has a rate of 0.35 air changes per hour or 15 cubic feet per person per minute whichever is greater. There are 3 types of ventilation: natural, spot, and whole house. While you'll likely need a contractor to install a more complicated system, the steps below will make you an informed consumer when you decide which system is right for your house.

Instructions

Natural Ventilation

1. Check the temperature outdoors.

2. Turn off your central heating and cooling system if the outdoor temperature is comfortable or in the direction of comfort (ie, if your home is too warm and it's cooler outside or vice versa).

3. Open a window or door.

Spot Ventilation

1. Use in conjunction with another ventilation strategy.

2. Install or turn on fans in the kitchen and bathroom for appropriate levels of ventilation.

Whole-house Ventilation

1. Hire a HVAC contractor who specializes in installing energy recovery systems - not all of them know how to do it.

2. Select the appropriate type of system.

3. Install vents in living room and bedrooms where people spend their time. Also, kitchen, bathroom, and perhaps the utility or laundry room where moisture and pollutants are generated.

4. Use existing duct work to save on installation costs.

5. Make ducts as short and straight as possible.

6. Use the correct size duct for the room size and type to maximize performance.

7. Seal all ducts with duct mastic (never use ordinary duct tape).

8. Insulate ducts in un-climatized areas of extreme climates.

9. Devise a system to prevent the ducts from freezing in cold weather.

Tips & Warnings

• Spot ventilation is generally already installed in your home and no action should be necessary other than turning it on in response to an obvious problem.

• When the kitchen or bathroom lacks a window, ASHRAE recommends intermittent or continuous ventilation rates 50 or 20 cubic feet per minute for bathrooms, and 100 or 25 cubic feet per minute for kitchens

• Houses should have a controlled ventilation rate of 15 cubic feet per minute (cfm) per person (According to standards published by ASHRAE). For example, a household of four requires 60 cfm. Another standard is 0.35 air changes per hour (ach). (You can quickly estimate the air flow in cfm needed to meet the 0.35 ach requirement by dividing the floor area in square feet by 20.) Remember these ventilation goals are for controlled ventilation, not spot or natural ventilation.

• If you select a system using high quality fans, make sure to get one with low energy use and low noise emissions.

• Installing a timer with your system can save you energy making it run only when you are at home or only when it's needed. However, people generally can't gage air quality very well; so, avoid manual controls. However, sensors that monitor indoor air quality are available in more sophisticated system.

• This system is unpredictable and uncontrollable. You can't rely on ventilating a home uniformly.

• Incoming air is not filtered for moisture, pollen or other pollutants.

• Energy recovery systems require more maintenance than other systems including regular cleaning to prevent mold and bacteria and overall deterioration of the parts.

• Fireplaces, wood stoves and gas-burning appliances cannot function safely with an exhaust system. It can cause flue gases, including carbon monoxide, to spill into the living space. If you select this type of system, you can either not have a fireplace, wood stove or gas burning stove or install only sealed combustion appliances that draw air from outside.

• In a balanced system, backdrafting shouldn't be an issue. However, in reality, balanced forced-air heating systems can be difficult to achieve. A highly-skilled contractor must create a detailed duct design and careful installation. Once installed, they must adjust the system. Even then, someone closing a door between a supply and a pickup can disrupt the carefully balanced air flow.