Innovative Energy Engineering



Enclosure

The enclosure separates the inside (comfort) from the outside (rain, light, heat, cold, wind, moisture). Rain Control Layer, Thermal Control Layer, Air Control Layer and Vapor Control Layer should be continuous throughout slab, wall, and roof including all elements inc. windows and doors. The shape of the building should be functional and efficient. Large Floorspace-to-Enclosure (F/E) Ratio reduce up-front cost and energy consumption. To eliminate thermal bridges, continuous insulation is needed.

Walls and Roofs

Walls are exposed to rain water, wind and temperature extremes. Water exposure can be reduced with roof overhangs, which also serve as shading devices. Colors should be light to reduce expansion, contraction, material deterioration and heat gain. Brick, metal or cement board are good outside materials that can last as long as the building. Thermal bridges occur by wall openings, where floors or partition interface the perimeter, at receptacles, or any other penetrations.

Roofs keep water out by diverting water before it can penetrate the roofing material. Steep roofs with long-life roofing materials (slate, copper, or other corrosion-protected metals) can last many decades with minimal care. Typical flat (low slope) membrane roofs with exterior membrane only last 20 - 30 years with occasional leaks. If a flat roof is required, an inverted, or protected membrane, roof should be used. This membrane is protected from sun and temperature extremes.

Asphalt shingles, plastic membranes and other modern materials are not resistant to sun light and deteriorate. In addition, those roof materials are made of crude oil, which is expected to be expensive at time of replacement and are combustible. Disposal also is a concern since recycling of those is not easy.

Roofs should always be vented above the thermal and vapor barrier. This will allow any moisture (from rain, or vapor leaks) to dry out over time. If insulation is not sufficient, the heat escaping will cause snow to melt. This water will flow to the (non-heated) overhang, freeze, and will create an "ice-dam" that keeps water standing in a puddle on the roof. This water will penetrate the roof and damage it.

A reflective roof reduces summer cooling load. Less heat also extends roofing material life. Older roofs without vapor barriers benefit from black roofing material as it dries out the insulation that got wet from condensation. Some white roofs without vapor control layer failed because of that. But the failure was the lack of vapor control, not the color. The roofing designer should understand how the roof works and adapt the design appropriately. there is no actual heating benefit of black roofs in winter:

Foundations, Slabs and Basements

Foundations and slabs are not exposed to sunlight and large temperature extremes but exposure to moisture is nearly constant. Water should be diverted by trench drains and sump pumps. Coarse gravel under the slab and as foundation back-fill will break capillary effect. Heatloss depends on the distance from the surface to the outside. More heat is transmitted from the foundation wall that is just below grade and less from the center of the slab. Foundation insulation has to be installed on the vertical foundation walls and additional insulation "wings" at the foot of the foundation slow down heat transfer from the slab. Heat is directly lost to the ground, which acts as an infinite heat sink. Heat lost to the ground can't get recovered.

Basements moisture often is not caused by leaky foundations, but by condensation on cold surfaces. This problem is worsened by ventilating basements, which brings in new warm and moist air. Mechanical equipment in basements often creates negative pressure, "sucking in" even more outside air. Insulating the foundation walls and slab increases the surface temperature of the basement and prevents condensation.

Doors

Doors allow persons, goods and vehicles to enter and exit the building. Their size, number and location are determined by function and egress requirements (code). Doors rely on seals, which wear out, to prevent infiltration when the door is closed. When a door is open, infiltration is very high depending on wind and temperature difference (often 0.25 m/s - 50 fpm). Air locks or vestibules can reduce infiltration. Frames and doors have to be structural to withstand abuse. The required aluminum and steel should be thermally broken and any glazing should have a very low U-value. Even the best doors have a U-value of 0.5 W/K-m² (0.29 Btu/°F-ft²). Standard insulated doors may have U-values of over 1 W/K-m² (0.6 Btu/°F-ft²). In spaces designed for neutral pressure to outside, air curtain may reduce infiltration. the energy for the air curtain fans needs to be weighed against saved heating or cooling energy. HVAC load due to doors is significant.

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