Conditioned Attic Systems

A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic.

Conditioned attic systems. Hpca is a below roof deck engineered insulating system that dramatically lowers attic temperatures brings ducts into conditioned space and. One outdoor condenser and the air delivering indoor units which you have at least one of or maybe four. Seems to me the only reason to create a conditioned attic is to bring the hvac system and ductwork into the thermal envelope of the home. In what is turning out to be an unfortunate turn of phrase the terms unvented attics and unvented roofs have entered the lexicon.

Most of the heat generated in your home is coming from the roof and the attic adding heat gain to the upper levels. An outdoor unit which houses the fan condenser and compressor and an indoor unit which holds the evaporator and fan. Building america research has demonstrated unvented conditioned attics can substantially improve energy performance while allowing home builders. Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts.

Lstiburek s enthusiasm was rooted in his desire to bring attic ductwork inside a home s thermal envelope. If there is no hvac in the attic why not just air seal and insulate at the attic level much easier and less expensive. The condenser in your air conditioner works hard to get rid of heat and pressurize refrigerant for the return trip through your house. Among the early promoters of conditioned attics was joe lstiburek a principal of the building science corporation.

So why put an hvac system up in the attic at all. Attic hvac systems save space. These connect by a refrigerant line and a. The system consists of two types of units.

A lot of the blame for that goes to me and for that i am sorry. Unvented conditioned attics were quite rare before the 1980s. Unvented conditioned attics the preference for a large segment of the u s. Well mainly it s a way to save space.

Creating a conditioned attic without a hvac unit in the attic. The right terms should have been conditioned attics and conditioned roofs. This is very difficult for the system and the upper levels of most air conditioned homes experience unsatisfactory cooling. Most people desire cool homes for sleeping and bedrooms are often located on the upper levels.

An edited version of this insight first appeared in the ashrae journal.