Flat roof recovery board – Part II

In a previous article on flat roof recovery boards, we discussed the material composition of the insulative materials and some of the methods of installation.  Today we follow up on that topic, to discuss the thermal and vapor barrier qualities inherent in polyisocyanurate recovery boards and reduction of condensation at a roof assembly where temperatures between outdoor untempered air and indoor tempered air can vary widely.

Flat roofing recovery boards serve as effective thermal insulators, providing benefits in both cold and hot climates, such as Washington DC, which experiences cold winters and hot summers. In addition to their insulation properties, recovery boards can also help reduce the accumulation of condensation in situations where there are significant temperature differences between the outdoor environment and the conditioned indoor space. Here’s how recovery boards contribute to condensation control:

Thermal Insulation: Recovery boards have a high thermal resistance (R-value), which limits heat transfer between the interior and exterior of a building. In cold climates, recovery board can help retain heat within the building, reducing heat loss through the roof. Conversely, in hot climates / seasons, this extra layer of thermal resistance can reduce the transfer of external heat into the building, helping to keep the interior cooler.

thermal recovery boards

flat roof recovery board

Vapor Retarder: Recovery boards often have a built-in vapor retarder or act as a vapor barrier themselves. These layers impede the movement of water vapor through the roofing assembly, reducing the risk of condensation forming on cold surfaces within the roof structure.

Dew Point Control: Condensation occurs when warm, moisture-laden air comes into contact with a surface that is at or below the dew point temperature. Recovery boards, by acting as insulation layers, help maintain the temperature of the roof deck closer to the indoor conditioned space temperature. This minimizes the likelihood of the roof structure reaching the dew point and reduces the potential for condensation to form.

Proper Ventilation: Along with recovery board installation, it is important to ensure proper roof ventilation to facilitate the movement of air within the roof assembly. Adequate ventilation helps remove any excess moisture that may be present, further reducing the chances of condensation.

ventilation of recovery boards

It’s worth noting that while recovery boards contribute to condensation control, other factors such as proper design, installation, and maintenance of the roofing system also play crucial roles. Consulting with a roofing professional or engineer familiar with the specific climate conditions in Washington DC is advisable to ensure the roof assembly is appropriately designed and constructed to manage condensation effectively.

The upkeep, maintenance, and general care of flat and mansard roof systems should be driven by an understanding and passion for historical methodologies, waterproofing principles, engineering and building science. Washington DC, a city built with both vintage charm and contemporary modernities, residential and commercial buildings of substantial value. 

The roofs of these buildings are their defensive shield from the harsh elements of nature. To our clients, as well as all readers of this article and our blog, we emphasize the importance of quality construction and active building maintenance.  Our website includes informative resources you can use to understand and learn about best practices on preservation of your building.  If you are in need of further guidance on the roof and its associated systems for your Washington DC property, we are here to assist, where we can. Simply contact us or complete the webform below and drop us a line and we’ll respond if we can help.

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