How much insulation do I need on my roof? On flat or low slope roofs the insulation is usually installed above the roof deck and below the waterproofing layer. It is much easier to install and typically comes in 4′ x 8′ foam boards. Typically there is a state code that says if you remove all the roofing material to the roof deck, there is a minimum R value that needs to be installed. The number is typically around an R value of 25 in RI and 30 in MA. The insulation of choice for the industry is isocyanurate, which has an R value of approximately 5.6 per inch. Insulating a building should be looked at in its entirety, not just for the roofing. If the roofing material has an R value of 100 and there are windows and doors that let all the hot/cold air escape – then all the money spent on insulating the roof is wasted. R values between 18 and 25 are typical for normal commercial buildings. We see R values between 40 and 50 installed on freezers and coolers. Be careful if you have a freezer or cooler because there are special roofing details that many normal roofers (and many engineers and architects) may not be familiar with.
The National Roofing Contractors Association has a tool for figuring how much insulation should be used – see energywise.nrca.net. If you really want to run the numbers for the whole building then look for an environmental engineer in your area. An engineer will utilize software designed to analyze and propose a solution for the entire building, including the roof.
A good way to be sure the building is insulated properly is to have an expert infra-red company perform an analysis with an infrared camera from the inside of the building.
Recycling can be done on various materials. The topmost material in many roofing systems is rock. 1/2″ to 2″ diameter round river rock is used on ballasted roofs and pea gravel (1/4″ or so) is used on certain types of asphalt roofs. This rock is removed from the roof either by the roofer brooming it into bags and hauling it off or by using a vacuum truck that vacuums the rock through a large hose into a cannister on the back of the truck. Our company typically deals with vacuum truck companies and they find places to dump the rock, which is used in landscaping. If you have one of the roofs where the rocks will be removed you may be able to use the rock somewhere on the property or on another property for free.
Single ply membrane can be recycled. To do so requires the membrane (EPDM, TPO or PVC) to be clean, folded and stacked on trailers parked on the job site. Insulation can also be recycled. The issue with recycling insulation is that it needs to be whole, relatively clean and dry. The boards (typically 4′ x 8′) are stacked in the back of a trailer truck parked in the parking lot. As the trailers are filled they are replaced with empty trailers. Roofers may or may not want to recycle material. If the system is such that single-ply membrane was glued or fully adhered then the adhesive on the back of the sheet will not allow the EPDM to be recycled. Ditto for the insulation. If the insulation is mechanically fastened then the insulation boards may not be in good enough condition as it is removed to recycle. The stacking, folding and cleaning of the material is extra work for a roofing company. Roofers have to pay a recycling company to remove the material. If extra work for recycling plus the cost to the recycling company is less than it would be to put the material in a dumpster and have it hauled away then recycling is of interest to the roofer. If you as the building owner / property manager want to recycle if possible, make sure you specify that before taking bids. Talking to the roofer about recycling after the contract has been signed may well generate an increase in the cost of the job. For more information on recycling check out www.nationwidefoam.com.
There is a lot of discussion about “cool” roofing. Most of the discussion talks about how a roof that reflects most of the sunlight off the waterproofing layer of the roof is more energy efficient than a roof that doesn’t. So – white vs black. But it’s really white membrane (or coating) versus gray (gray membrane or even rocks) versus black (black EPDM or maybe modified bitumen). White roofing proponents make statements saying white is good for all environments. The opponents say basically there is a line across the country, north of which more energy is used heating than saved in the summer cooling. Another possible point in favor of white roofing is to cool cities in the summer (the heat island effect) despite any possible energy dollars lost in the winter. The US Dept. of Energy has a site that can also be utilized to see the differences of white vs black – www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htm. Our advice would be to install more insulation in multiple layers before you start looking for savings with a white or black waterproofing layer. Do some of your own research – with multiple sources – and then see if you have a preference.
Daylighting is the centuries old practice of lighting the interior of a building with openings in the structure. As this is about roofing we ignore windows and discuss skylights here. Using skylights to light an interior space can directly reduce the electricity costs. Skylights can also reduce the need to replace lights as they wear out, which for some building owners is a considerable expense. Other possible reasons to install skylights include studies that have shown natural daylight makes employees more productive and shoppers more prone to purchase. The Federal government offers a $.60 per square foot tax deduction for the current year (up to the installation cost) provided the skylights are partnered with sensors and controls on the interior electric lights. To obtain the deduction an engineer must certify the installation. Sensor and control costs may be partially offset by refunds from the electric companies.
Skylights come in different shapes, sizes and types. There are skylights with two domes (we recommend) and some with one dome (not recommended). The domes can be clear, glazed or prismatic. The clear domes let the light through unfiltered. The glazed domes dim the light slightly. The prismatic domes are made of little prisms that offer two advantages. The first prismatic advantage over regular skylights is that sunlight can be caught and utilized when the sun is lower in the sky. The second prismatic advantage is the light coming through all the prisms is diffused and distributed evenly throughout the interior space, without any traveling bright spots that normal skylights may have.
Skylights come in many different sizes. Solar tubes are approximately 6″ to 12″ in diameter. Other sizes vary from 4′ x 4′ to 4′ x 6′ and can ramp up to about 50′ x 100′ or even larger. Setting up skylights to maximize light isn’t simply a matter of just buying and installing the largest skylight possible. The layout of the interior needs to be taken into account. Skylights over storage rooms don’t make sense. The position of the interior rooms, high storage racks or other types of partitions should be taken into account when placing the skylights. Skylights can also be utilized as smoke vents – which open automatically should the heat in the building reach a certain temperature in case of fire to let the smoke out. Some smoke vents work with a fusable link and springs that cause the smoke vent domes to pop open. A newer version smoke vent supposedly has the domes melt when they reach a certain temperature.
Installing the skylights is not a trivial expense. The skylights are typically craned to the roof, a hole is cut in the roofing material and then the roof deck itself. The hole in the deck typically needs some type of reinforcement. Making a hole in the roof over an office area can be messy and disruptive (imagine cutting a hole in a concrete deck over someone’s desk). Once the skylight curb and domes are installed on the hole the roofing needs to be re-flashed or made water-tight around the new skylight curb. If a skylight is installed into a finished area the interior must be repaired around the skylight and probably re-painted.
There are some skylight calculations being done that attempt to determine the payback period of the skylight investment based on reduced electrical usage. If a calculation is done for you, make sure all installation costs are included, not just the cost of the skylights themselves.
Skylights have a very low R-value. Wasco makes a unique one called Ecosky3 that has an insulating gel between the double domes if loss of energy is an important consideration.
There are many different types of solar panels. Some are hard panels that are silicone based, while some are flexible thin film. As of this writing the silicone based panels are more efficient but are a little more expensive. The more panels put on the roof the more electricity gets generated, so the incentive is to squeeze as many panels on the roof as possible. Find a reputable solar dealer and they can probably offer you multiple business models to pay for the panels. Options are available from you buying the panels outright and taking the deductions (Federal 30%, possibly state) to the solar provider leasing the roof, selling you the electricity at a set price for a period of years and then taking the deduction. Things to look for from the solar provider are web based software to show the electricity output and some sort of error notification if one of the panels fails (which may knock out a whole string of panels).
If you decide to put the panels on your roof there are some impacts to the roof. The panels are typically warranteed for twenty years. If your roofing system will not last twenty years then it should be replaced before the panels are installed. Installing a new roofing system after the panels are installed is much more expensive. Can the cost of a new roofing system required for the installation of the solar panels be included in the Federal or State deduction? We have heard it may be – consult your tax adviser as it could be a substantial amount of money.
The waterproofing layer should be relatively tough. If a single-ply membrane is used it should have a reinforced scrim in it (all PVC and TPO membranes have to be reinforced, while EPDM comes in reinforced and non-reinforced). Aisles should be left between the panels to allow HVAC technicians to service machinery. Depending on the traffic in these aisles walk pads or walkways should be installed. The fewer penetrations the panels make the less likely the roof is to leak. If the panels rest on the roof there should be a buffer or slip sheet between the panels and the waterproofing layer. It makes sense to allow for a few weeks to elapse between the installation of the new roof/waterproof layer and the installation of the solar panels. This time allows for some rain to make sure the roofing is leak free before being covered by the panels.
If you have a manufacturer’s warranty on a roofing system (and we highly recommend this) the roofing system should have been inspected upon completion. Many manufacturers require a re-inspection upon completion of the solar installation (for a small fee). One issue in installing the panels is how does a roofer repair a leak. If the roofer can’t get to or find the leak some of the solar panel(s) may have to be removed and later re-installed. Manufacturer’s warranties do not cover this expense (termed overburden).
Another issue to be concerned with is crushed insulation, especially where panels are loaded to the roof or at pathways between rows of panels. Extra foamboard and plywood should be used during the insulation to prevent the roof installation from being crushed.
Storm Water Retention:
What happens to the water draining from your roof? The water either goes into your plumbing waste system through interior roof drains or into the landscape around the building via scuppers, gutters and downspouts. Any water coming down the side of the building should be controlled to prevent erosion of the wall or erosion at the bottom of the wall. Re-using that rain water is gaining more interest. It can be piped to water the landscape or even stored in a tank and re-used for non-potable water uses inside the building. See the following site for a more complete description of the issues – en.wikipedia.org/wiki/Stormwater.