Lstiburek Perfect Roof

There is no potential for condensation until interior moisture levels exceed 45 rh at 70 f during the coldest month.

Lstiburek perfect roof.

Simple physics complicated language. The perfect wall roof and slab building science podcast dr. One of the great features of these systems is that the water control layer is also the assembly air control layer and vapor control layer a k a the perfect roof see bsi 001. There s been so much stuff said about roofs that you sometimes lose perspective.

That is one of the neat ideas of lstiburek s perfect wall. Joseph lstiburek talks about the not so controversial ways to maximize the efficiency and airflow of your roof and attic. All insulation above roof deck the big deal with unvented roof assemblies is to control condensation or moisture accumulation on the underside of the roof sheathing. Insulation air conditioning heating and forced air delivery systems have all changed the physics of how houses work.

R 46 unvented roof assembly two layers of r 6 5 inch rigid insulation yielding a total combined thickness of 2 5 inches. Lying down it makes the perfect slab. Tilted it makes the perfect roof. The biggest benefit of the pmr is that the membrane is well protected.

Joe lstiburek talks about enclosure design principles for energy efficient houses. Personally i don t view it as inverted. The perfect roof the perfect roof is sometime referred to as an inverted roof since the rainwater control layer is under the insulation and ballast i e. The first control layer is for bulk water or liquid water redundant terms used to make a clear distinction between water and water vapor which is the third control.

Two layers are preferable to one layer due to increase in air flow resistance. But stay tuned for the perfect wall austin blog posts next week. Houses didn t used to rot but too many of them do now. Here s a wall diagram to whet your appetite.

Layers of rigid insulation have staggered joints to facilitate airtightness. Unvented roof here again the choice of what insulation to use and whether to install it over or under the roof deck depends on the condition of the present roof the depth of rafters the r value you must attain and cost. Joseph lstiburek is the founding principal of building science corporation. I ve been thinking about this concept for years but i m finally building a perfect wall house.

The physics doesn t change with floors or roofs so to get the perfect roof just pitch the wall same for the slab.