That is an interesting question that might have a different response depending on your location.
Let'sbegin by reviewing how heat is transferred through roofing. Heat travels on light rays (radiant), ina vapor or liquid (convective) and through solid objects (conduction).
- When we say a roof is energyefficient we are speaking of its ability to reduce all three.
- In cold weather states conductive heatmovement is not a function of roof coverings.
All climate zones are concerned with radiant andconvective heat transfer with regards to the roof structure.
In a predominantly cooling climate we should select a roof that reduces the impact of all three typesof heat transfer since the sun radiates heat to the roof coverings which heat the roof structureconductively causing the attic to heat up. The heated air pressurizes the attic and may force the heatedair into the habitable structure through convection.
So when we think of a roof covering as energy efficient we are almost always talking about howeffective it is at reducing transfer of radiant heat into the attic via conduction or convection.
Asphaltshingles are somewhat effective if you purchase a solar reflective roofing shingle. A percentage ofradiant heat is bounced back into the atmosphere.
Unfortunately there is still enough heat that warmsthe roof and surrounding structure making the attic hot during sunny periods.
Since the asphalt shinglesare in direct contact with felt underlayment and the felt is installed directly over the roof sheathingthe entire structure is within a few degrees of the asphalt shingle temperature. Once the sheathing isheated up through conduction it warms up the attic which in turn warms up the living spaces throughconduction and convection.
Concrete shingles are much more effective at reducing all three types of heat transfer.
- Concrete tilescan be reflective in color which reduces heat gain.
- Since they are elevated they actually allow the heatgain to be vented so the roof structure has significantly less heat gain.
- The heated air under the shinglesis vented through the ridge cap helping to keep the roof structure cool.
So strictly from an energyperspective concrete tiles are more energy efficient than asphalt shingles.
Other factors to consider
There are other mitigating factors in choosing between asphalt shingles and concrete tiles.
- Concreteis fire proof, wind proof, brittle to walk on and more expensive up front.
- Asphalt shingles are cheaperinitially, safe to walk on (weather permitting), wind resistant and easily repairable.
You can install aradiant barrier under the roof structure (not on the floor of the attic) that will improve the energyefficiency of the roof assembly using asphalt shingles.
- A properly install radiant barrier can reduceradiant heat gain and vent conducted heat through the roof venting system.
- Remember in order that a radiant barrier be effective the reflective surface must be exposed to an airgap.
Selecting a contractor
Whichever way you go select a qualified contractor, verify their references, licensing and insurancecoverage.
- If you go with a cement roof make sure that they have done a lot of cement tile roofs.
- Talk toprevious customers to see how their experience with the contractor went.
Don't disqualify a contractorthat has had a complaint if they handled the complaint and the client was satisfied. Anyone that hasbeen in business for any length of time will have had complaints, many unjustified.