Q: Can you explain the advantages and/or disadvantages of the pre-planted tray systems versus the traditional green roof systems?
Durhman
|
A: Good question! With more and more players entering the green roof arena each day, it's good to know what the various differences
and similarities are between the two types of installation systems and which one is right for your building.
An integrated, continuous, or "traditional" green roof system is actually built right onto the rooftop in an intricate system
of layers. Typically these systems tend to be more ecological and can be more economical if the contractor has previous experience.
A continuous green roof is usually more flexible in design, utilizing walkways or detailing around roof penetrations. Typically,
there is 12 percent to 16 percent greater storm-water holding capacity in a continuous system. And because a continuous system
allows for more flexibility in design, with fewer restrictions regarding configuration, it may be the preferred system to
use in conjunction with solar panels or other rooftop energy solutions.
A modular system can be assembled on-site and applied over the top of an already-existing rooftop structure. There are different
types of modular systems, and these answers may vary per manufacturer, but generally a modular system can be used on sites
where craning soil may be difficult or expensive and may be more economical in smaller projects, such as terraces or in residential
applications. The modular system can be pre-planted, or installed on the roof and filled on-site. These systems allow a facility
manager the option of moving vegetation patterns around the roofscape and allow easier removal to access the roof membrane
if necessary.
Both systems use drought-tolerant plants, usually succulents, and lightweight growing media, which is blended and engineered
for vegetative roofs.
Whether using a modular or a continuous green roof system, checking the warranty is always recommended for specific applications.
— AD
Q: Is it possible to use an acrylic coating over silicone coatings?
Knowles
|
A: The spray polyurethane foam (SPF) industry does not recommend coating over silicone with coatings other than silicone. As
stated in the Spray Polyurethane Foam Alliance's technical document AY 102, Guideline to Elastomeric Coatings Used in SPF
Roofing, "Other coatings will generally not adhere to silicone. Silicone may be used as a top coat over elastomeric coatings."
I chair the ASTM subcommittee on SPF roofing (ASTM D 08.06) and have been a member, former chairman, and SPFA staff to the
SPFA technical committee since 1987. I am not aware of any successful applications of other coatings over silicone; however,
I am aware of one acrylic coating that has been developed to adhere to silicone coatings (manufactured and marketed by National
Coatings). But I do not have any field performance data to share on the success of the coating.
Is it possible a primer could adhere an acrylic coating to silicone coating? Yes, but the burden of proof is up to the supplier
to provide a documented field performance history of successful recoat applications. I strongly recommend that your customer
obtain performance history of the primer mentioned going back at least five years demonstrating that it can adhere acrylic
coatings to silicone coatings. — MK
Q: How does solar energy work?
Burdic
|
A: A solar module (also referred to as photovoltaic or PV) converts light directly into electricity by means of a solar cell.
Built of razor-thin layers of semi-conducting material, every cell is a power generator. To make one PV module, 48 cells to
72 cells are connected to each other. In general the front part of the module is covered with a hardened glass plate while
the back section is usually protected by a plastic film. When light falls on a PV module, the radiant energy is converted
into direct current (DC), which is then converted into household-compatible alternating current (AC) by means of an inverter.
— BB This month's questions are answered by Angie Durhman, green roof program manager for Tecta America, spray foam consultant
Mason Knowles, and Brad Burdic, manager of sales and marketing for Ecostream. If you have a question specific to green, spray
foam, or solar applications, please email RSI Editor-in-Chief Thomas Skernivitz at tskernivitz@questex.com
.
