Uninsulated Flat Roof

The target should be to achieve a u value of 0 25w m2k or better.

Uninsulated flat roof.

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. 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. As a rule any roof with a pitch below 10 is classified as a flat roof. 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.

To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. Proper ventilation in flat roofs. In most cases there will not be a loft in a building that features flat roofing. 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. The typical u value of an existing uninsulated flat roof is 1 5w m2k. 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. U value has an inverse relationship to r value.

This means that your approach to insulation will differ from a standard pitched roof. R value measures how well certain building insulation materials can resist heat. When determining how much insulation you need don t guesstimate calculate. The slate is new and the flat roof is good for another 5 7 years.

Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point. 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. Ventilation is necessary to allow moisture accumulated inside to escape. If you don t want to put vinyl backed insulation in your roof what other options are there.

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. It also lets hot air escape in the summer. When you have an un insulated roof you have to live with rather uncomfortable room temperatures inside the home. Reduce extreme temperature fluctuations inside your home.

It should be of the maximum available thickness. 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. But a preinstalled membrane may be even more effective at removing condensation.