Replies

1. GBA Editor
   Martin Holladay | Jul 23, 2013 11:50am | #1

   Ritu Goyal,
   Are you the architect or builder? Is this the first time you have designed a building or specified building materials?

   Chandigarh, India, has a a humid subtropical climate with very hot summers (up to 41°C, or 106°F) , mild winters (lows of −1°C, or 30°F). The average annual rainfall is 1110 mm (44 in.).

   I would recommend roof insulation of at least R-30 (about 7.5 inches or 200 mm of EPS, or about 5 inches of 125 mm of polyisocyanurate).

   Your should choose a roofing with high solar reflectance (ability to reflect sunlight, measured on a scale of 0 to 1) and high thermal emittance (ability to emit thermal radiation, also measured on a scale of 0 to 1).

   You should choose glazing with a low solar heat gain coefficient (SHGC).

   Of course, I don't know what building materials are available in Chandigarh. Good luck.

2. 
   ritugoyal | Jul 23, 2013 01:25pm | #2

   Sir, I am civil engineer.
   Yes, this is the first time I am handling.
   Can you suggest me some name of glazing too?

3. GBA Editor
   Martin Holladay | Jul 23, 2013 01:37pm | #3

   Ritu,
   I imagine that your window supplier or glazing supplier can describe what types of glazing are available in India.

   Here in the U.S., new commercial buildings use either double glazing or triple glazing. These are referred to as "insulated glazing units" (IGUs). They are rated by the manufacturer according to several criteria; the most important criteria are U-factor, solar heat gain coefficient (SHGC), and visible transmittance (VT).

   In your climate, you want a low U-factor, a low SHGC, and a high VT. These criteria cannot all be simultaneously optimized, so you will need to accept a compromise. You glazing supplier or manufacturer can help.

   For more information, see All About Glazing Options.

4. 
   ritugoyal | Jul 23, 2013 02:22pm | #4

   thanku so much sir any type of new intervention if possible so that i cud apply like waste material

5. Expert Member
   Dana Dorsett | Jul 23, 2013 03:10pm | #5

   The optimal type of insulation material vary by roofing type, (Is the roof going to be metal? Ballasted EPDM membrane? Tile? or....???) , and the choices of either may be cost-driven.

   EPS and polyisocyanurate are commonly used under membrane roofing in commercial buildings in the US, but may or may not be cost effective in India. From a price/performance point of view it's not always the better option, and the price is sometimes affected by the international oil price, since the manufacturing feedstocks are from petroleum. These materials are manufactured in and available in India, but being a net-importer of oil, I would expect the cost to be on the high side.

   But there are also domestic manufacturers of mineral wool insulation which may be both less expensive and more appropriate (and unlike foam, is fireproof.) See:

   http://lloydinsulations.com/UploadedFiles/Resources/LIL-Products-Rockloyd_Building_Insulations_Res25.pdf

   The primary feedstock for this type of insulation is the slag left over from steel making- a substantial industry in India. I don't know whether that makes a significant difference in the domestic pricing of the finished insulation product, but in the US mineral wool is usually cheaper than EPS or polyisocyanurate.

   Depending on the building size, use, and shape, going above some optimal thickness in insulation can begin to increase the annualized energy use. (This is almost never the case for a single-family house, but fairly common with commercial buildings.) The thermal mass of the roof itself will also affect the optimal amount, as will the amount of heating or air conditioning used. It's not a simple model, and whether 200mm of EPS or mineral wool is the "right" amount from an energy use or cost point of view is not entirely clear. In most of the US 125mm of continuous insulation between the structural roof deck and the roofing above would meet current code minimums on a commercial building, but would not be adequate for most single family residential buildings. Under the IECC 2012 code, in US climate zones 1 & 2 (the climates most similar to northern Punjab) only require R20 (125mm of EPS or high-density mineral wool, or 150mm of mid-density mineral wool.) See the Table 402.2 on page 12 of this document: http://www.energycodes.gov/sites/default/files/becu/2012iecc_commercial_envelope_BECU.pdf

   Without simulating the building, and without knowing the relative material or energy costs, it's probably reasonable to assume that 100mm of EPS or mineral wool would be a reasonable minimum, and 200 mm would likely be a maximum (and may even be beyond the optimum, depending on building use, and the rest of the building design.)

6. 
   user-1087436 | Jul 23, 2013 09:38pm | #6

   My rupee's worth: a Google search for "mineral wool slag wool India" comes up with plenty of hits. For example,

   http://www.minwool.com/insulation.htm