Green and Energy Issues

Q. How environmentally “clean” is this tile? Does it have any harsh chemicals associated with it? Can we use this roof for water catchments? How safe is it to drink this catchments water, if filtered correctly of course. Is there any adverse chemical runoff associated with this roof? We have land that is going to be used for organic farming with the roof used for catchments.

A. Because our tiles are made from sand, cement and oxide coloring, there are no chemicals added and nothing that would prevent you from using them for catchments with proper filters.

Q. We are going to put on a new roof with a light weight tile. I would like to place a radiant barrier underneath the tile but the roofer says not to do. He says it will burn the felt underlay. Is this correct?

A. I’m not sure what evidence your roofer is citing to support his claim but I have not heard of any studies that have arrived at this conclusion. I have had roofers express concern with radiant barriers used under asphalt shingles but a tile roof assembly offers far more air circulation so I don’t see the radiant barrier as a significant risk. Since you are obviously making considerations for heat reduction, you should also incorporate some other features into your tile roof. A number of studies have shown conclusively that a tile roof installed on an elevated batten system with good ventilation is the coolest roof that you can install. Most of the benefit is gained by the increased air flow between the tile and the roof deck.

Q. What level of energy cost “penalty” am I likely to incur by going with a Dark Charcoal Blend Slate roof over a white color slate tile?

A. While color is an important factor in the thermal transfer of heat into the attic, it is not the only one. The thermal mass of a concrete roof tile slows heat transfer, the air space between the tile and the deck acts as an insulator, and the air permeable nature of individual tiles (air movement through the gaps between the tiles) all contribute to lowering attic temperature. Also, standard insulation of the attic space plus radiant barriers and attic ventilation contribute as well. The impact of color is not quantifiable specifically other than to say that white performs better than charcoal in heat transfer studies. To measure specifically, the other factors mentioned must be taken into account. The fact that current home construction involves generally up-to-date insulation does mitigate the effects of the color of the roof tile. The rule of thumb is to select the color most consistent with the architectural intent of the home since the energy savings on a properly insulated home would usually be negligible from color change.

Q. I’m starting to think about roofs for construction of a new home. Would there be an insulation difference if using a flatter, slate-type tile as opposed to one with a bumpier shape. It seems there would be less air circulation under the slate type.

A. You are correct in your thinking that a profiled tile will allow more circulation between the roof deck and the tile underside which, in turn, will reduce the heat gain into the attic. The effect may be further enhanced by installing the tiles on a counterbatten or elevated batten system. Studies in Florida have shown up to a 10% reduction of ceiling heat flux by using this system. The elevated batten system has the added advantage of reducing the chance of roof leaks and extending the life of the underlayment and batten system.

Q. In order to enhance energy efficiency I am considering using a Radiant Barrier OSB Sheathing on our house. The roofing I will be using is a lightweight shake style tile. Do you know if this type of sheathing will have any negative effects on the tile and if you have any recommendations regarding the use of this product?

A. It is quite common to use OSB with radiant barriers as a substrate for concrete tile application. We are not aware of any problems associated with this application and, given the physical properties of the tile; it is not likely that it would be affected by the reflected heat than can affect other materials, such as asphalt and chemical based materials.