Drive to save energy is causing failures.


The principles and dilemmas of designing durable house envelopes for the North.

Starting from the premise that condensation in the building envelope is a prime cause of its deterioration, the mechanisms that cause condensation are discussed and control measures explained. The conflicts that arise between some of these measures, the probability of achieving them under realistic construction conditions, and the possible need for fail-safe provisions should complete success not be achieved, are described.

Home insulation.

Investing in insulation is a good way to reduce energy consumption in the home. The homeowner must determine where adding insulation will be most cost effective. Attics are usually the place to start, followed by floors and walls. Since there is a wide variety of material on the market, thedo-it-yourselfer must choose carefully and install them with proper regard for ventilation and vapour barriers. Even if the work is performed by a contractor, the informed homeowner will benefit by his knowledge of materials and procedures.

High and dry

Failure to understand the principles appropriate to a particular roof makes it all too easy to introduce condensation problems, often serious ones. A distinction between surface condensation and interstitial condensation is made. Before attempting work on any roof it is necessary to determine how the roof is designed to work. If the principles are wrong, the whole design should be checked and if necessary corrected.

Precast panel wall assemblies

Discusses control of condensation, and moisture transfer through walls. Various air pressure barriers are suggested to control leakage. One-, two- and three-stage joint methods of wall construction are compared.

Reducing moisture problems

Describes the physics of moisture in the home. Suggests four basic strategies for dealing with excess moisture buildup in the home: 1) minimise the entry and release of moisture, 2) protect building components with vapour barriers, 3) remove water vapour with ventilation or dehumidifiers and 4) raise theinside surface temperature of windows.

Condensation potential in wood-frame walls

Test structures were constructed near Madison, Wis, USA and Gulfport, Miss, USA for exposure of eight types of insulated wall panels at controlled indoor conditions and typical outdoor weather conditions. Panels were instrumented with moisture sensors and tested without and with penetrations (electrical outlets) in the indoor surface. Continuous internal vapour barriers effectively prevented cold weather condensation in all panels. Installation of an electrical outlet changed moisture patterns in both the cold winter climate and the hot, humid summer climate.