Archive for 10+ Year Solution

Previous steps:

If you are at this point you have hopefully read through our recommendations on how to check out your existing roof and prepare it to receive a new roof. Choosing what type of roofing system involves a lot of factors – existing substrate, functional requirements, warranty requirements, cost sensitivity and building codes. A 10+ year system would involve installing a new comprehensive waterproofing layer, possibly with additional insulation or substrate separation layer at a low cost. The difference between a 10-15 year warrantied system and a 20-30 year warrantied system is the 20-30 year usually has a thicker waterproofing layer, may have added redundancy at key future failure points like flashings or the roof edge, may require it be the only roofing system installed and the warranty costs more per square foot. 90% of our customers are happy with the 10-15 year warrantied system.

Functional requirements:

  • Is it important to reduce heating and cooling costs? It may not be if you have a warehouse or shop type environment. If it is important then how much will more insulation reduce the heating and cooling bills? There are different ways to figure this out – use EnergyWise from the National Roofing Contractors Organization or hire a professional to check the roof and/or the whole building. The best advice you can buy will be just an estimate. There are too many variables for someone or some computer program to say exactly what the savings for increased rooftop insulation are. The roof isn’t the only place that can lose hot or cold air. If you are serious about saving the energy bring in an infra-red camera and check the entire structure as well as any machinery in place. The building codes for New England for new roofs generally require an R value between 15 and 22, depending on how much window glazing there is in the walls and the location of the building. Isocyanurate insulation is the most cost effective insulation and it has an R value of 6 per inch. If the R value in your roof is close to the building code requirements it could be years before the return on investment from increased insulation is seen. Thicker insulation costs more in insulation material, thicker wood blocking at the perimeter of the roof to match the thicker insulation height and longer fasteners to secure the insulation to the roof deck. Check what you have existing on the roof and ask your roofer for a separate cost for thicker insulation.
  • Does the roof or area receive lots of foot traffic – choose strong insulation/underlayment materials and a tough waterproofing layer with redundant layers. Install walkpads, walkway rolls or pavers as well.
  • Are strong winds possible? This could occur from being near an ocean, lake or large empty field. The building height and the presence of a parapet wall (and how high the parapet is) around the perimeter of the building also can generate more uplift on the roofing system. If there is more wind make sure the manufacturers warranty specifies a greater wind speed so the design of the roofing system is appropriate.
  • Will the roof deck structure be able to support the new roofing system plus any snow load – if there is any question a structural engineer must be brought in.
  • Is there a plan to cover the roof with solar panels – again the structural load must be checked and the roofing system should be one that lasts a longer time. The solar panels may require a white roof to either cool down the panels for efficiency or actually utilize the reflected sunlight to convert to electricity.
  • Have you considered adding skylights – doing it during re-roofing saves on installation costs. Skylights can allow most lights to be turned off in the daytime. There are new types worth checking into (prismatic lenses, solar tubes).
  • Is the existing drainage adequate – if not add more downspouts, scuppers, interior roof drains, crickets (raised areas) to force water away from ponding areas. Tapered insulation may be needed on the entire area to generate correct drainage.
  • Are there areas in the walls that open up to create negative pressure on the roof (truck bay doors) – install an air barrier and extra insulation/waterproofing attachments in those areas. Make sure all roofing material will be secured to the roof deck appropriately.
  • Is a vapor barrier required – is the area a pool, sauna, hothouse, uses lots of moisture, etc. – check with a professional.
  • Are grease or oil products exhausted onto the roof – use sandboxes around the fans and special protection for single-ply membranes (PVC is much better than EPDM or TPO)
  • Is your building insured by FM Global – they will need to be involved in the re-roofing process.
  • Is the building a freezer or cooler – in addition to extra insulation certain roofing details need to happen at the roof edges and around all penetrations – make sure the roofer knows what they are doing or money will be wasted through continual energy loss.
  • Are there special color requirements for the perimeter metal that shows from the ground – Toyota dealers require all metal to come from one place – special orders – long lead times.
  • Are there areas where snow/ice can slide off the roof and cause injuries – discuss snow guards/rails. This is especially important on roofs with a pitch greater than 1″ in 12″ like metal roofs covered with single-ply membrane or coatings that offers less resistance to sliding snow.
  • Waterproofing layer – What are the choices?

    The 3 main choices for a waterproofing layer in New England are asphalt built-up, single-ply membrane and modified bitumen. Will a coating last 10+ years – maybe, but since we haven’t seen one do that we are not speaking to that option. We also haven’t seen a spray foam roof last 10+ years in New England – so we aren’t speaking to that option either.

    Built-up roofing

    The built-up asphalt roof waterproof layer is really multiple layers of asphalt and felts (usually 3-5 layers). Built-up roofs are usually covered with small rocks (gravel) if the slope is not steep or the wind is not strong. The main advantage of these roofs is the redundant layers of waterproofing. The disadvantage to the owner is the cost and the use of torches and kettles. The cost is high due to the cost of the asphalt (competing with roads and road repairs). Other factors that drive up the price is that there are fewer roofers that want to install these types of roofs, which are tough on the installers, and fewer roofers have the knowledge to install these kinds of roofs.

    Modified Bitumen roofing

    A modified bitumen waterproofing layer consists of asphalt derivatives that come in 3′ wide rolls. There is usually a base sheet and a cap (top) sheet that make up the system. The cap sheet comes in different thicknesses. Both the base and cap sheets can be attached to the substrate in different fashions (torched, mechanically fastened or adhered). There are two types of modified bitumen – APP and SBS. The APP type is primarily asphalt. The SBS type is a mixture of rubber and asphalt. The most important difference is that APP is not flexible in normal New England winter temperatures so we do not recommend using this product. The SBS type remains flexible in sub-zero temperatures so is more appropriate for New England. Both the base sheet and the cap sheet are typically twice as thick as single-ply membrane. If a roof is to receive heavy foot traffic or heavy wear then this may be a good choice due to the extra thickness. The downside of the modified roof is that it costs more than single ply, since roll widths are only 3′ wide there are more seams to seal correctly (usually with a torch), and it is more difficult to seal around penetrations with the thicker membrane.

    Single-Ply Roofing at a High Level:

    A single-ply membrane performs the waterproofing with a single sheet of material. The material is either rubber-based (EPDM) or plastic-based (TPO or PVC). The material comes in varying thicknesses – .040″ thick to .090″ thick. EPDM is usually black but can come in white (much more expensive). EPDM can come with a fabric mesh embedded in the rubber (called reinforced) or not. EPDM rolls are joined together with seam tape (double-sided tape) within the last 15 years and prior to that adhesive. TPO and PVC are plastic based but chemically different from each other. Both TPO and PVC always have the mesh fabric embedded to provide strength. TPO and PVC usually come in white, gray and tan (sometimes other colors). TPO and PVC seams are heat welded with hot air. The advantage of a single-ply waterproofing layer is cost and flexibility. It also comes in wide sheets which require less seams and is easier to flash around penetrations (less chance of applicator error). The disadvantage is that it can be punctured more easily than modified bitumen or built-up roofing waterproofing layers. If you want a white roof then choose TPO or PVC. If you are comparing prices of EPDM to TPO/PVC, then to compare it properly the EPDM should be reinforced EPDM.

    PVC is generally the most expensive, followed by TPO, reinforced EPDM, then non-reinforced EPDM. The thicker the membrane the higher the cost

    Substrate Options:

    Between the waterproofing layer and roof deck there are layers of materials that can be installed. Some layers are mandated by the building code, some are mandated by the waterproofing layer manufacturer. Vapor barriers try to keep moisture from inside of the building diffusing and condensating into the roofing layers above the deck. Air barriers attempt to stop any gusts of air from pushing on the roofing system from the bottom and could be tied into the air pressure systems of the building. Insulation prevents hot and cold energy leaving or entering the building. Coverboards are dense materials that are used just under the waterproofing layer to protect the roofing system from traffic or next to the roof deck to protect the roofing system from fire.

    Vapor barriers:

    The vapor barrier is intended to stop moisture from condensing in the roofing layers. Vapor generally flows from an area of high to low vapor pressure. The vapor pressure depends on the temperature and the amount of relative humidity. Certain recreational and industrial activities result in a high interior relative humidity (pools, fruit storage, processes with lots of open liquids, etc.). If your building generates a high relative humidity then a vapor barrier should be considered upon re-roofing. The best way to prevent vapor transmission through the roofing system (and other building components) is through adequate ventilation. Many times the practicality and cost of doing this ventilation is prohibitive and a roofing vapor barrier is the next choice. If a vapor barrier is installed its effectiveness is lessened as screws that hold down roofing material over the vapor barrier puncture it. Roof penetrations also must be sealed to prevent vapor from escaping around them. If you have high humidity, the roof deck itself should have some protection from underneath. We have seen steel deck rust from underneath and eventually require replacement. For a more technical discourse on vapor control please refer to “The Manual of Low-Slope Roof Systems” by C.W. Griffin and Richard Fricklas.

    Air barriers:

    The air barrier is intended to stop air from moving through the roofing system. It is generally to stop air pressure from inside the building from pushing up on the roofing material. This is particularly important where there are alot of openings in the walls. On single-ply roofs that have the membrane mechanically fastened an air barrier can also help stop air from being pulled from one area and pushed into another. If you are re-roofing a building there should be some experience as to the air flow and what roofing systems are/were on the building. If the building is strictly climate controlled or could result in negative pressure on the roof then an air barrier should be installed. The air barrier should be sealed around all penetrations.

    Coverboards for Fire Protection:

    If a fire occurs below the roof deck the most important thing the roofing assembly can do is to not spread the fire. The first line of defense is the material the roof deck is made of. When re-roofing the building it is highly unlikely to consider replacing the entire structural deck component just in case a fire might happen. The roof assembly is a different story. The most fire resistant material should be next to the roof deck. The most common material we see is a gypsum like board from Georgia-Pacific called Dens-Deck. There are other competitors that also perform well in a fire. With the more stringent enforcement of fire prevention systems and practices, and insulation materials tested and fire rated, we see less coverboards immediately above the roof deck specified by architects, consultants or roofing companies.