Lstiburek Perfect Roof

Lying down it makes the perfect slab.

Lstiburek perfect roof.

Tilted it makes the perfect roof. 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. 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. Simple physics complicated language.

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. Lstiburek s commitment to advancing the building industry has had a lasting impact on building codes and practices throughout. The biggest benefit of the pmr is that the membrane is well protected. Joseph lstiburek talks about the not so controversial ways to maximize the efficiency and airflow of your roof and attic.

There s been so much stuff said about roofs that you sometimes lose perspective. 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. That is one of the neat ideas of lstiburek s perfect wall.

If all of the insulation is on the top of the roof sheathing this is pretty much a no brainer. 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. R 46 unvented roof assembly two layers of r 6 5 inch rigid insulation yielding a total combined thickness of 2 5 inches. There is no potential for condensation until interior moisture levels exceed 45 rh at 70 f during the coldest month.

Joe lstiburek talks about enclosure design principles for energy efficient houses. Houses didn t used to rot but too many of them do now. The perfect wall roof and slab building science podcast dr. Layers of rigid insulation have staggered joints to facilitate airtightness.

But stay tuned for the perfect wall austin blog posts next week. Two layers are preferable to one layer due to increase in air flow resistance. Cost aside the most straightforward route is spraying closed cell polyurethane foam on to the underside of the roof deck. Here s a wall diagram to whet your appetite.

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.