Attic Insulation with Desiccant

Abstract

A method of reducing the amount of cooling energy required to cool a building is provided. The method includes disposing a porous insulating material substantially covering the ceiling in the attic space of the building to a substantial depth. The porous insulating material includes a desiccant. The method further includes permitting the desiccant-bearing porous insulating material to adsorb water moisture from the attic space and then permitting the adsorbed water moisture to desorb from the desiccant-bearing porous insulating material into the enclosed room of the building, whereby the temperature of the desiccant-bearing porous insulating material is reduced, resulting in a reduction in the amount of cooling energy required to cool the building.

Description

FIELD OF THE INVENTION[0001]The present invention relates to insulation products, such as batt and loose-fill insulation, and board products such as duct liner and duct boards, having better thermal properties for cooling dominated climates.BACKGROUND OF THE INVENTION[0002]Most residential construction includes an attic space between the ceiling and the roof deck. The structure that supports the roof and provides the ceiling plane is often constructed with pre-assembled wood trusses. The structure can also be built on-site using traditional ceiling joists and roof rafters. Properly insulating the attic is essential to reducing home energy consumption (“building load”). Thermally isolating the attic from the rest of the house also increases the comfort of the living space below in both winter and summer.[0003]Attic ventilation serves two purposes: prevention of moisture condensation in the winter and attic cooling in the summer. Ventilation during the heating season removes moisture-...

AI Technical Summary

Benefits of technology

[0010]A method of reducing the amount of cooling energy required to cool a building is provided. The building generally includes an enclosed room partially defined by an outer wall, a horizontal upper wall plate, and an attic space exposed above the upper wall plate. The attic space is defined by a ceiling of the room and a roof of the building. The method includes the steps of (1) disposing a porous insulating material substantially covering the ceiling in said attic space to a substantial depth, the porous insulating material including a desiccant, (2) permitting the desiccant-bearing fibrous insulating material to adsorb water moisture from the attic space, and (3) permitting the adsorbed water moisture to desorb from the desiccant-bearing fibrous insulating material into the enclosed room, whereby the temperature of the desiccant-bearing fibrous insulating material is reduced resulting in a reduction in the amount of cooling energy required to cool the building.

[0011]In the more preferred embodiments of the present invention, the desiccant is a silica gel which is added to loose-fill or batt insulation used in attics in climates dominated by a cooling. As a result of the heat energy in the attic expended in evaporating the moisture in the silica gel in the insulation in the summer cooling season, the heat flow from the attic into the living space is reduced. The simulated, calculated net energy savings in a 1500 square-foot house in Miami with a 20 percent silica gel content (by volume) in R30 insulation can potentially reduce net annual energy costs by about $50.00.

[0013]In computer simulation models, it was determined that negative heat flux flowing from the living space into the attic increases due to higher thermal conductivity of the present invention's desiccant insulation mixture containing fiberglass and silica gel in the winter climate. Additionally, negative moisture fluxes flowing from the living space into the attic were reduced to a very small amount due to the high level of moisture in the desiccant insulation mixture in the winter. These results were compared to a fiberglass only insulation control in the attic space during the same climate conditions. In the summer months, the fiberglass insulation with silica gel resulted in a reduced positive heat flux flowing from the attic into the living area, in the model, since heat energy in the attic was being used to evaporate moisture from the desiccant. It also resulted in an increase in the positive moisture flux flowing from the attic into the living area due to extra moisture from evaporation from the desiccant into the living area. In the cooling dominated climate of Miami, the addition of desiccant to the attic insulation reduced the total roof energy load in the computer models of this invention. In heated dominated climates like Baltimore, Minneapolis, and San Francisco, the addition of desiccant to the insulation increased, rather than decreased, the total roof energy load in computer simulations.

Problems solved by technology

Despite the many attempts to properly insulate attics, the attic space of most buildings is perceived as a source of a nuisance.

In summer, the heat build-up in the attic space increases the cooling load.

There is a higher air or relative humidity at the surface of the wood framing materials which results in moisture being desorbed by wood attic framing materials.

In modern residences, the challenge of achieving a continuous air infiltration barrier and thermal insulation barrier at the interior ceiling level is especially difficult.

When water from melted snow runs out over the unheated eave portion of the house, it freezes and expands, often driving its way back up the roof and between shingles.

4 Roof shingle temperatures will be higher during no-wind conditions leading to a higher heat load on the attic.

Due to limited attic space, adding more roof insulation may not always be a feasible way to reduce the total building loads in many instances.

Images