Insulation Between Ac Ducts In The Attic

In last week s blog i discussed the practice of burying attic ducts in deep insulation since burying ducts is simply one of several ways to address the energy waste associated with the decision to locate ducts in a vented unconditioned attic it s worth taking a fresh look at all of the possible solutions to the attic duct problem.

Insulation between ac ducts in the attic. Put it in an attic full of blown insulation and you re. Attic hvac systems save space. Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts. The condenser in your air conditioner works hard to get rid of heat and pressurize refrigerant for the return trip through your house.

Sometimes the insulation is inside the ductwork. Table 1 shows effective r values for 8 inch round ducts at three attic insulation levels and three duct insulation levels r 4 2 r 6 and r 8. Our heating and ac ducts are 100 within the thermal envelope in the floor trusses above our insulated basement. Because the moving air is in the ductwork for only a short period of time it does not need the insulation r value the attic floor requires.

Flexible ductwork comes with different insulation r values. So more would help. An outdoor unit which houses the fan condenser and compressor and an indoor unit which holds the evaporator and fan. The effective r value of a buried duct installation depends on the size of the ducts the r value of the duct insulation and the depth of the loose fill insulation.

2 duct leakage must be no higher than 1 5 cfm25 per 100 square feet of conditioned floor area. In more cases than not a 3 ton ac with the ducts in the attic has a ton or so of load that s just from the location of the ducts in the attic and the associated duct gains leakage etc. Well mainly it s a way to save space. Why is condensation on ductwork a problem.

The second question gets a yes if the buried ducts meet even more stringent requirements. What would be bad is if the duct work is flex duct and gets mashed under the weight of the added insulation on top of it. And 3 the sum of the ceiling insulation above the duct and the duct insulation must equal the prescriptive r value for ceiling insulation. First water dripping off of your ducts and onto your insulation can cause the insulation to compress which decreases it s r value or ability to insulate.

When water condenses and drips into your attic or home it can cause a some serious secondary problems. 1 the air handler must be inside conditioned space. Other times insulation may be on the outside. The remaining 2 tons of capacity is at least 1 5x oversized for the actual 1 load.

Why is this a problem. So why put an hvac system up in the attic at all.