When replacing your roof, consider using cool roof materials. Roofing materials that reflect the sun's energy will help keep the indoor temperature down, reducing the heat load and requirements of your cooling system in the warmer months. Reflective or light colored roofing materials are particularly recommended in hot and humid environments.
Cool roof materials take advantage of the reflective properties of light colored materials. Dark materials absorb the energy from the sun and transfer this heat into your home. If your home has dark shingles, you may be running your air conditioner more than necessary, consuming extra energy and paying higher utility bills.
According to the Florida Solar Energy Center, a white ceramic tile or white metal roof is best. They typically last for 30-40 years compared to the 15 years, typical of asphalt roofs. White reflective roofs may lower attic temperatures by up to 30 degrees F, therefore reducing the requirements of your cooling system greatly. Cool roofs also tend to be more durable than conventional roofing materials, extending the lifetime of your roof.
Consider This:
A few of the most important factors to consider when replacing your roof are the material, insulation below, ventilation, and drainage. A consumer's guide to buying a new roofing system is provided by the National Roofing Contractor's Association. It is recommended to contact a professional who is familiar with roofing systems as well as any local codes, to help determine the type of roofing materials most suitable for your needs.
Drainage: Your Gutter System
The purpose of gutter systems is to collect rainwater from the roof and drain it away from the building and foundation, preventing moisture problems and ensuring greater durability. The picture to right shows gutters plugged with debris and serving as planters.
Improper drainage may lead to water damage to the foundation, when the water is let drain straight down rather than being diverted away from the structure. Various problems that may arise due to a gutter system not functioning properly include freezing, damage to the soffits, discoloring of siding materials, soil erosion and problems with the foundation and basement.
Radiant Barriers
A radiant barrier should be installed to reduce heat gain during the warmer months and heat loss in the colder months. Radiant barriers reduce the heat transfer across the air space between the roof deck and attic floor by reflecting radiant heat.
How Does it Work?
Solar energy absorbed by the roof causes the material beneath it to radiate heat into the attic. With a radiant barrier installed on the attic floor, the heat radiated from the roof is then reflected back up, keeping the insulation cool. This then also keeps the rooms below cool by minimizing the heat that moves through the insulation, to the rooms below the attic.
A radiant barrier consists of a thin sheet or coating of highly reflective material, usually aluminum, which is applied to a substrate material. The substrate may be kraft paper, plastic film, plywood sheathing or air infiltration barrier material.
Radiant barriers must have a reflectivity of 0.9 or higher and a low emissivity, of 0.1 or lower. Reflective is a measure of how effective the material is in reflecting heat (.9 = 90% reflected) while emissivity is the ratio of the radiation emitted by a surface to the radiation emitted by a blackbody (a theoretical object that emits 100% of the thermal radiation) at the same temperature.
Installation
There are various ways a radiant barrier may be installed. Preferably for retrofit construction, the radiant barrier is attached to either the faces or bottoms of the rafters or top chords of the roof trusses. In both configurations the space between the roof sheathing and the radiant barrier provides a channel through which warm air can move freely. If the radiant barrier is reflective on only one side, the reflective side should face toward the main attic space, since a surface facing downwards is less likely to have dust settle on it.
In order to function properly, a radiant barrier must face an open air space.
The barrier can alternatively be laid atop the existing attic insulation, with the reflective side up. Although this is the simplest method, there are several disadvantages: Dust will settle on it, decreasing the radiant barrier's effectiveness; traffic (if the attic is used for storage) will damage it; and moisture can be trapped where it will soak the insulation and potentially lead to mold problems. Also, kitchen and bathroom vents and recessed lights should not be covered with the radiant barrier
A radiant barrier should not be confused with a vapor barrier. The radiant barrier must allow the passage of water vapor. If there is no vapor retarder at the ceiling, moisture from the living space may condense and could freeze on the radiant barrier of an attic floor. In areas of extreme cold or long periods of cold, a layer of condensed water could build up. If your radiant barrier is applied to the roof, it is not necessary that the material allow the passage of moisture.
The general guide to follow is to have the gutters sloped a minimum of 1 inch for every 40 feet of run. Gutters will be sized according to the roof drain area and should be evaluated by a professional.
Seeking the Help of a Trained Professional
There are many projects you may be able to complete to improve your home. However, some projects may be too complex or dangerous for the untrained person to perform. It may be necessary to bring in a certified energy auditor or other specialized contractors. Multifamily rehabilitation projects in particular may require the help of a trained professional. ENERGY STAR provides information for Finding a Professional Energy Efficiency Contractor.
Insulation Basics
Insulation is one of the most effective ways to save energy. Heating and cooling costs comprise more than 50% of the energy consumed in a single family home. Adding the recommended levels of insulation will save energy, reduce utility costs and improve comfort. Proper installation is critical; gaps and compressed areas will dramatically reduce effectiveness.
Insulation provides additional benefits including noise reduction, fire resistance and safety. Factors that affect the performance of insulation, and should be considered when choosing the appropriate type for the job, are insulating capacity, fire resistance, moisture control, convective heat loss, settling and loss of insulating capacity.
