"Passive-Active" Ventilation (AKA "Suckulation")

Goals of Innovation: The goal was to build a sustainable home utilizing time-tested techniques for managing the hot, humid south Louisiana climate. Prior to the availability of cheap electricity, homes built in this climate incorporated numerous features to take advantage of natural ventilation. This home is innovative in that many older, mostly forgotten traditional features were married to a new, innovative design, which takes advantage of the home site, modern building techniques, and materials. There is perhaps no new residential construction in Louisiana today without mechanical air-conditioning. This home appears to be the only off-grid, full time residence in the state.

Description: The home is sited to take advantage of the prevailing breezes and this, with the seven clerestory awning windows below the roofline, actively pulls air up, through, and out of the house. The breezes over the home's roofline create a venturi effect. The windows on all sides of the home allow the occupants to direct and maximize air flow and fine tune ventilation. The design is so successful that even when there is no breeze the house actively creates ventilation through the stack effect, much like the flu of a wood burning stove. Warm, humid air is drawn to the ceiling and out of the home. There are no horizontal ceilings to trap the warmer, more humid air. Instead all ceilings are pitched so warm air rises towards the seven elevated awning windows and exhausted with no mechanical assistance, relying on the venturi effect.

The architect calls this effect "suckulation" because the result of the design is that air is literally sucked through and out of the home without the need for mechanical devices. The architect contends that most designers think of how to bring air in to the building for ventilation. The real secret for ventilation is designing to create negative spaces high on the leeward side of the structure. Hot air rises and vent out through those negative openings. Design to help nature do what it wants to do. The magic is to know what nature wants to do.

Obstacles: No obstacles were encountered. The design calls for off-the-shelf materials readily available at any lumberyard or home improvement center. The builders enjoyed creating a structure that represents a mix of local tradition and innovative design. In addition this home is a showcase for the builders attention to detail and craftsmanship.

Cost Information: The cost was no more than any home that would have many windows and a cathedral ceiling.

Additional Benefits/Drawbacks: There are multiple benefits of a design, which allows for non-mechanical air exchange. The obvious one is no energy consumption, which decreased the cost for PVs and batteries. Less obvious benefits include: the increase in natural light from the seven awning windows; less need for the oven hood vent; the absence of noise from fans or blowers; and the ability to draw cooler air from lower in any room at any time and direct the warmer air up and out of the home. The design is successful enough that during the hottest, most humid months of the year the homeowners must use a light blanket at night.

No drawbacks have been identified.

Double Air Space Roofing System

Goals of Innovation: The homeowners hoped to minimize heat gain from the hot south Louisiana sun.

Description: Removing heat from the interior of a building is much more difficult than preventing the initial transfer of the heat. Due to low-cost taxpayer subsidized electricity; current local building techniques rely much more on mechanical removal of heat as opposed to preventing the solar radiation heat gain in the first place. Traditional building techniques (prior to the creation of air-conditioning) concentrated on averting heat gain from the sun.

This innovative home combines traditional techniques with new approaches and modern materials to effectively minimize solar heat gain. The roofing innovation features two air spaces: one between the steel roofing and the decking and one between the radiant barrier and the rafter insulation. From exterior to interior the order in which the materials are placed is as follows: Steel roof, 2' X 4' wooden "sleepers" (creates air space along with the roof corrugations), 30 lb. felt, 5/8' CDX plywood decking, radiant barrier, rafters (12' on south side, 10' on north side), an air space between the radiant barrier and the high density fiberglass insulation, Tyvek secured with nails and caulked to the bottom of the rafters, and lastly luan plywood. The finished edges of the luan was beveled with a router then pickled to "open up" and accentuate the natural light from the north side cathedral ceiling awning windows.

This innovative construction assembly combats heat gain all three ways it is transferred: conduction, convection, and radiation.

Obstacles: It was necessary to special order the high-density fiberglass insulation and the 26-gauge, commercial grade steel roofing material.

Cost Information: The increased labor cost was in the order of 25%. Material costs were increased by the use of the Tyvek, high-density fiberglass insulation (with shipping as an additional cost), and the need to special order the steel roof. This type of roof has higher ridges and deeper valleys, which require 30% more steel than conventional steel roofing. The increase cost of materials over a conventional roof is estimated to be about 40%.

The increased cost of this roofing system was largely offset by not needing supplemental mechanical ventilation to remove heat. The cost for the materials and labor to install mechanical ventilation for an off-grid house is compounded by the need for additional photovoltaics and batteries. At the time of construction the average cost for installing a renewable energy PV system in the U.S. was approximately $5.10/watt.

Additional Benefits/Drawbacks: Additional benefits include: Esthetically the homeowners do not need to endure the noise of a mechanical ventilation system; the interior of the home was spared the need for added soffits, electrician costs and materials; and the innovative design combines efficiency and simplicity. The builders, homeowners, and "tour groups" continue to be impressed with the maintenance-free nature of this simple, yet effective innovation.

The combination of the home's roofing system as well as the natural "suckulation" design result in a home that feels as though it is mechanically cooled during the hottest, most humid months in our sub-tropical climate. During the hottest part of the year the homeowners open all of the windows at night. The home cools. During mid morning, when the outside temperature begins to rise the windows are closed. With the windows closed warmer air is not drawn into the home and with the innovative roofing system there is little if any solar radiation heat gain. The home remains comfortable throughout the hot daytime and evening hours. In late evening the windows are opened again. This cycle is not only effective for temperature control but the sloped ceilings and air movement prevents mold and mildew formation.

Except for the initial increased costs of labor and materials no drawbacks have been identified to date. There are people who enjoy the sound of rain on a roof those people will find this innovation blocks that sound.