Uninsulated Flat Roof

An uninsulated roof has a u value of approximately 2 5 w m2k however adding insulation can achieve a value of 0 18 w m2k.

Uninsulated flat roof.

U value has an inverse relationship to r value. However in many situations the insulation may need to be primarily or entirely below the flat roof membrane and between the roof joists if so what are the best options. Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point. When you have an un insulated roof you have to live with rather uncomfortable room temperatures inside the home.

The slate is new and the flat roof is good for another 5 7 years. The type that is right for your flat roof insulation job depends upon the state of the roof expert opinion on the best type and your budget. If you don t want to put vinyl backed insulation in your roof what other options are there. The target should be to achieve a u value of 0 25w m2k or better.

How dr pstop can help the answer is a product called dr pstop which is a felt like material with a rubber backer that can be applied to the back side of metal panels that will trap the moisture as the condensation forms. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. Reference table for u values u value is the coefficient of transmission i e the transmission of heat through the materials which compose the building s envelope or outer shell. The higher the r value the greater the insulation performance.

In most cases there will not be a loft in a building that features flat roofing. If moisture has nowhere to go it will gather around joists and eventually undermine the insulation. Flat roofs do not have eaves so there are no soffits holes on the underside to allow air flow. We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof.

When determining how much insulation you need don t guesstimate calculate. It should be of the maximum available thickness. Proper ventilation in flat roofs. While insulation for a flat roof is expensive and can account for as much as 25 of the total installation cost there are a number of important benefits to having it in place.

But a preinstalled membrane may be even more effective at removing condensation. Ventilation is necessary to allow moisture accumulated inside to escape. Reduce extreme temperature fluctuations inside your home. As a rule any roof with a pitch below 10 is classified as a flat roof.

Unvented flat roofs a technical discussion flat roofs have often been built with the insulation all on top of the vapor closed drainage plane as this avoids dew point condensation issues inboard of the roofing. It also lets hot air escape in the summer. The typical u value of an existing uninsulated flat roof is 1 5w m2k.