Will A Metal Roof Save On My Heating And Cooling Bill?

       

The answer to this question is yes and no; it will save money on your cooling bill, but the effect will be negligible on your heating bill.

 In addition to no maintenance costs, a metal roof, especially aluminum, can lower your demand for air conditioning. According to the Florida Solar Energy Center, installing a simulated cedar-shake aluminum roof can reduce heat gain from the roof down through the ceilings by as much as 34 percent. Steel roofs, although not as efficient as aluminum, are also better than asphalt shingles. A metal roof cools down in five minutes once the sun sets.

An Energy Star rating for all roofing products is based on TSR (total solar reflectivity). Classic black asphalt shingles will have a TSR of only 0.05, while a quality aluminum roof will have a TSR of around 0.40. The larger number will mean that the roofing materials remain cooler and less heat will be radiated down through the ceilings to the living area. Also the underside of the aluminum metal surface has a lower emissivity (the ability to emit heat) than asphalt shingles, so less heat radiates downward.

Follow this link to an Energy Star roof calculator: http://www.roofcalc.com/    before making any roofing decision.

Metal roofs can save you as much as 20% on your summer utility bill by keeping your attic several degrees cooler. You can increase the savings by adding a radiant barrier under the metal roof to reflect even more heat rays.  A radiant barrier http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11680  can also be installed inside the attic as a retrofit on any metal or asphalt shingle roof. Avoid a horizontal application because dust from your insulation will reduce the radiant barrier’s effectiveness over time. The best application will be between the rafters up against the underside of the roof.

So the answer to this question is yes, a metal roof can reduce you energy bills. I will add that a radiant barrier alone will reduce your energy bills as will lighter color asphalt shingles or shade from large trees. A new roof can be an expensive proposition and it is always wise to calculate your ROI (return on investment) http://www.greenandsave.com/master_roi_table.html  on any improvement.

Attic stairs

Insulating and air sealing the attic is of utmost importance here in the south. R-38 insulation is recommended in both flat and vaulted ceilings, but it won’t do much for the air infiltration/exfiltration that takes place between your attic and your living space. Blown cellulose does air seal slightly because of its weight, but it will not truly define the thermal envelope of your home. Top plates of walls, knee walls and HVAC penetrations are big culprits for energy loss, but one overlooked energy drain is the attic access. The photo below is of an uninsulated attic access taken with an infrared camera.

Many older homes here have a small (24”X24”) attic hatch that is often hidden away in a closet. These are relatively easy to deal with by weather stripping and gluing batt insulation to the attic side of the panel. If they are too light to fully compress the weather strip, adding another layer of drywall or plywood to the back side will help. The large pull down stair cases or “disappearing stairs” as architects like to call them can be tougher to deal with, but when properly sealed will make a tremendous difference.

Most builders or insulation companies will simply place an R-13 batt between the stairs and the cover panel. This makes little sense when you have an R-38 attic, but it is common. There are several commercial options available to seal and insulate the access that work very well, but some are rather expensive. An attic tent is good for providing an air tight seal, but has little R value. There are foam options that both air seal and insulate, but you want to be sure that what you install is tall enough on the attic side to hold back 13 inches of blown insulation (an insulation dam). If you are the least bit handy, building an attic “coffin” is the cheapest and easiest approach. One sheet of cheap plywood or OSB will do the job and you will find that it is much more rigid than the commercial options.

The coffin is a simple 5 sided box with a lift off lid. The weight of the top is heavy enough to compress the weather stripping and give a good seal. Be sure to make the sides of the box tall enough for the stairs to fold up in! This may sound like common sense, but it was my first mistake. Once you have sealed the attic hatch you can proceed with air sealing and insulating the remainder of the attic.