20 inches 508 mm by 30 inches 762 mm minimum.
Attic furnace need to know.
Having your hvac system in your attic isn t dire though you ll need to do some work to keep your air conditioner or furnace system running as efficiently as possible.
Attic furnaces save living space on main floors.
Poor insulation is usually the culprit although if you enter the attic on sunny winter day your attic space can be warmed by the sun more than your furnace.
In most codes this means an opening not fixed window to the outside.
For homes built more recently that fold the attic into the home s thermal envelope the problems are less pronounced and you ll be better able to take advantage of the benefits such a location can offer.
Understand the efficiency math today s standard furnace is about 80 efficient meaning 20 percent of the fuel energy goes up the chimney.
That means you have higher energy costs and less efficiency since you re blowing the air down instead of allowing it to rise naturally.
Attic furnaces are becoming more common in both residential and commercial buildings.
Most of the issues that furnace might experience in an attic are due to extremely cold weather in this poorly insulated space.
The total drop in efficiency can be up to 35.
Unless your roofing system has insulation on the roofing deck and is designed without ventilation your furnace should not be heating your attic.
Since the staircase to the attic can act as a chimney for the fire to quickly spread it s necessary to have a secondary point of egress or exit.
Finally you need to be aware that when you are installing a furnace in an attic you may be restricted to certain models.
The first and possibly most important thing is to make a commitment to yourself to change your hvac filters regularly.
Many high efficiency furnaces are not recommended for attic installation and you may find that there is a drop in efficiency when the furnace is located in an unconditioned space like your attic.
But you can get furnaces all the way up to 98 5 efficient which is listed on the product information as the afue annual fuel utilization efficiency rating.
High efficiency furnaces aren t usually recommended for an attic.
While the traditional spot to locate a residential furnace has been the basement there are many reasons why putting it in the attic is more convenient.
Access opening and an unobstructed passage way to the appliance furnace in attic area must be provided and be adequate in size to allow removal of the largest appliance installed.
If you place the furnace in the attic then you must install the infrastructure in the building to force the warm air to the bottom floor.
It should be easy to see that there are many potential drawbacks to consider when locating furnaces inside of an attic.