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.