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All of these features must work together to achieve a healthy home.
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In older and more traditionally constructed homes, air leakage into and of the building (infiltration and exfiltration) is very high. The warm air which escapes from the building is replaced with cold air, which must be heated. It is common in non-energy efficient homes to have a complete air change (of the total house volume) occur 2-3 times per hour. In the quality energy efficient home, which has been "tightened" to drastically reduce this form of heat loss, the air change rate is frequently only 1/10th of an air change per hour (some 20 to 30 times less).
The result…a much smaller heating system than usual will be required. And it will operate much more efficiently. Further, the occupants will be more comfortable as annoying drafts and heat stratification will essentially be eliminated.
Airtightness is achieved by the knowledgeable builder who will carefully craft the house with appropriate quality materials. Gaskets, weatherseals, caulks, virgin polyethylene vapor retarders and other special materials will be properly applied.
The energy efficient home of today has substantially reduced the natural (but wasteful and uncomfortable) flow of air into and out of the home. Therefore a controlled ventilation system will be included to insure the indoor air quality is comfortable, healthy and of the correct moisture level.
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A unique feature of contemporary energy efficient homes is the addition of a thoughtfully designed and carefully installed controlled ventilation system. For many years public and commercial buildings have been required to have such systems. Today they are not only available for the residential market…they are an integral part (indeed some believe the very heart) of the energy efficient home.
Two basic types of controlled ventilation systems, and various forms of each, are possible in today’s homes. The first is known as a direct ventilation system. This allows for a constant measured flow of stale indoor air to be exhausted from the building at a designed flow rate. At the same time a similar amount of fresh air is introduced into the building. Both the “pick-up” and “introduction” points are carefully sized and selected for maximum effectiveness and minimum discomfort. In the direct process no attempt is made to recover any of the heat from the exhaust air stream.
The second form of controlled ventilation has heat recovery. Several, unique arrangements are possible. The most common is an Air-to-Air Heat Exchanger. This simple machine has two low wattage fans and a two stream air core. The out flowing air passes through one side of the core and the incoming air passes through the other. Neither is allowed to contaminate the other. However, heat transfer takes place whereby the incoming air is pre-heated with the outgoing air. These devised are approximately 70-80% efficient. That is to say they save about 70 – 80% of the outgoing heat which is transferred to the incoming air.
Another form of heat recovery ventilator is the Air-to-Water system. In this unit the outgoing warm air will pre-heat the domestic hot water for the home. Other systems are available including integrated systems that will clean the air, heat and cool the house.
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One of the major causes of damage to a house is excessive moisture. Moisture can be present in homes in three forms: as a vapor, liquid or solid. All homes will have moisture in the vapor form and we measure this as the indoor relative humidity (RH). Liquids are all about the home (bathing, cooking, clothes washing, paints, etc.) Solid moisture (frozen water), is not common about the home except in food freezers.
When these vapors, liquids and solids are kept under control (in the right quantities and locations), they are not a danger to the building. When out of control they can and will cause serious damage.
Of the three forms of moisture, liquids and solids are usually controlled best. As we see them we remove them. However, excessive moisture vapor is not as easy to detect. Frequently, we do not realize we have high RH until damage becomes obvious (mildew in the closet for example). A more serious problem is moisture vapor being transported into the exterior wall cavity or attic where it may condense into water. In these locations water can cause extensive structural damage long before it is recognized. This can and does occur in many homes due to poor moisture control design and construction techniques.
Moisture vapor is generated at the rate of approximately 25 pounds (about three gallons), by an average family of four, per day. When this is added to the moisture already in the indoor environment the (RH) may exceed the recommended levels of 40-60%.
An average 2,000 square-foot house at 70 deg. F and 40% RH will have about a gallon of water in the air at all times. All homes have heat loss, mostly through the walls and ceiling. With that heat goes moisture vapor. Perhaps as much as the equivalent of a half gallon of water or more per hour. If this vapor reaches the dew point (condenses) in the wall cavity or above the ceiling, it has the potential to cause serious water damage directly or by supporting mold, mildew, dry rot or other fungi which will cause health problems to the house and its occupants.
The quality builder of energy efficient homes will carefully install high grade vapor retarders (vapor barriers) or special gaskets as the primary defense against moisture migration into the walls and attics by air movement and diffusion. Further, they will design and install an appropriately sized and balanced ventilation system to control the indoor RH at a safe level at all times. It is not possible to assure a home safe from moisture damage without these two measures. Demand them both to protect the investment in your home.
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Radon is an inert gas which has been linked to cancer (normally lung cancer), in humans. It is thought to be the second highest source of lung cancer after cigarette smoke. Because Radon gas can’t be seen, heard, felt, touched or tasted, many people falsely consider it to be of no serious consequence. However, both the U.S. Surgeon General and the U.S. Environmental Protection Agency have issued warnings and guidelines to protect humans from Radon. So have many other countries.
Radon is a naturally occurring radioactive gas which is produced in the normal decay process of uranium and radium. Most all buildings will have some trace amounts. Some areas have greater amount than others. Unfortunately, there is no reliable test of the soil to determine how much Radon is present prior to enclosing a building. We are only able to accurately measure this gas after the building has been completed.
Radon gas is measured in a unit called picoCuries per litre (pCi/L). The U.S. EPA has set a maximum of 4 pCi/L (in air) as the probable safe level for humans in homes. Buildings with readings above this are candidates for some form of mitigation according to this schedule.
4-20 pCi/L … Action to reduce this level to 4 or less within a few years, sooner if at the higher end.
20-200 pCi/L … Remedial action to reduce this to 20 or less within several months.
above 200 pCi/L … Action to reduce far below 200 within a few weeks. Consultation with State or local officials suggested to consider possible temporary relocation.
Mitigation techniques after construction are usually costly, not easy to accomplish and may not be successful. It is far better to design and construct a system that can be engaged if the completed residence tests in a range requiring action.
Knowledgeable contractors will design and build with the possibility of mitigation being required. The techniques are proven, quite simple and low cost. Most importantly, you will have the peace of mind that should mitigation be required it can be accomplished quickly and most always successfully.
There is a mistaken belief, held by many, that tight energy efficient homes have higher levels of Radon than leaky non energy efficient homes. Several independent studies conducted by the EPA, Bonneville Power Authority (BPA), and most recently Cornell University, to name a few, have examined this issue. Each has found no correlation between elevated Radon levels and energy efficient building techniques. In fact, there is evidence to suggest that tightening a building will reduce Radon levels.
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Heating & Cooling the Energy Efficient Home
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The contemporary energy efficient home will receive about one third of its heat from natural solar gain. This will be from normal amounts of quality windows placed mostly on the south and southeasterly quadrants of the home. Lesser amounts of windows would normally be placed on the west and north sides.
A second third of the heat required, on an annual basis, will be from what is called occupant gains. That is heat given off by humans (and any pets) directly plus all associated heat gain from such things as cooking, lights, refrigerators and freezers, TV, radio, bathing, motors, etc.
The final third will be required from more traditional means of heat generation. However, the size of this auxiliary heating system will be substantially smaller than in the traditional non-energy efficient home. For example it was common to provide a 125, 000 BTU output heating system in a 2,000 square foot home just ten years ago. Today’s energy efficient home of that size will require only 50,000 or less depending upon the climate and the specific design of the building.
While cooling systems are not common in the cold climate home, if desired that system will be 40-50% smaller in the energy efficient home.
Over the past 10-15 years drastic changes and substantial improvements have been made in the heating and cooling systems for the energy efficient home. Smaller central heating system using natural gas, propane and heating oil now are common in the range of 30,000 BTU’s and up. Equally important these units are much more efficient, often better than 90%.
These new central heating systems are available as sealed combustion units. That is to say they receive combustion oxygen directly from outdoors. Many offer direct venting where chimneys are no longer required… even for gas and oil units. Rather than conventional chimneys a small exhaust pipe can be placed directly through the side wall of the building. These are frequently only 2-5” in diameter.
One of the most common mistakes in the traditionally constructed non-energy efficient home was to drastically over size the heating system. This resulted in wasted energy by systems that did not function efficiently.
The quality energy efficient builder of today has excellent computer software at their disposal to expertly analyze the heating (and if you desire cooling) needs for your new home on a room-by-room basis. You will be given appropriate options to meet your fuel, distribution technique and budget preferences.
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The Energy Efficient Home
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The energy efficient home has been called by several names: Low Energy, “EE”, Micro-Load, LO-Cal, etc. Probably the most frequently used name is and least understood, is the term SUPERINSULATION. It is quite clear this name is most closely associated with energy efficient homes in North America.
Several excellent books have been written to describe the form of building system we call superinsulation. Most who have written about it explain that certain characteristics must be present to qualify such a home as being superinsulated. These including: relatively high levels of insulation, airtightness, controlled ventilation and very low heating (and cooling) costs.
Many experts do not like the term superinsulation. They suggest that the emphasis is on the word insulation, and lots of it. Rather, they argue, the term superinsulation describes a unique building system. These experts are right on both counts.
There are many people, including many builders, who think an energy efficient house is accomplished by simply adding more insulation. Nothing could be further from the truth. And this approach could create serious problems to your health and home.
The truly energy efficient building requires: high levels of insulation, airtightness, controlled ventilation, and a competent building contractor who will design this house as a system and build it with expert craftsmanship at the right price.
The energy efficient home, by whatever name, will have these qualities:
1. Very low heating and cooling costs.
2. No architectural constraints
3. No micro or macro climate requirements
4. Simple construction techniques
5. No uncomfortable drafts (or heat stratification)
6. Controlled ventilation (safe and healthy indoor air quality)
7. Controlled relative humidity
8. Ample amounts of natural light through high quality windows.
9. Quiet
10. Naturally cooler is summer, warmer in winter
The quality energy efficient building contractor understands all of the above and is capable of designing and constructing such a home at a fair price.
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Selecting a Qualified Energy Efficient Building Contractor
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Selecting a qualified building contractor who is experienced and completely knowledgeable in the field of energy efficient residential construction, is not an easy task.
Consider these facts: The cost of a home is probably the most expensive purchase most of us will ever make. Most of us have very limited knowledge of building science and technology. Those who may have a limited background in building may not have kept up with appropriate and proven energy efficient building techniques, materials and products. Few home buyers even know a builder, qualified or otherwise.
How best to choose a qualified building contractor? First a decision must be made as to a general contractor vs. several sub contractors. The general contractor will be responsible for the complete design and construction of all phases of the residence. The general contractor will offer the buyer a complete package and be responsible for the entire project from start to finish.
When several sub contractors are hired, the owner usually acts as the general contractor. This practice should not be adopted unless the owner has: considerable time and inclination to devote to this major undertaking, knowledge of quality sub-contractors who can meet your time schedule, the freedom to be "on site" almost daily to answer the many questions from the "subs", approve "change orders", be a "gofer" and generally pick up all loose ends from the building inspector to the utility company.
Further, acting as your own general contractor, may not be acceptable to your Mortgage Company or bank unless you have proven experience. This may also require a “construction loan” which some lenders do not care to make.
Assuming you wish to engage a general contractor you should consider the following before signing a contract.
1. Visit recent homes built by the firm you are considering.
a. Speak with the current owner to learn of any dissatisfaction as well as qualities they liked in that builder.
b. If possible discuss the energy efficient characteristics of the home with the owners. What are their utility bills? What heating system do they have? How does the ventilation system work?
c. Would the owner recommend this builder to you?
2. Does your bank or mortgage company know this contractor from first hand experience as a quality energy efficient builder?
3. Does the contractor offer "full service" including design?
4. Where did the contractor receive his training? Does that person (and his or her employees) attend seminars, workshops or courses on energy efficient building techniques and materials?
5. Is this contractor insured? For what and how much? Have they had law suits against them? For what reasons? How have they been resolved?
6. Can this contractor offer you choices of:
a. Foundation, wall and roof systems.
b. Different insulation materials
c. A choice of controlled ventilation systems.
d. A choice of heating systems/fuels
e. Air conditioning if desired.
7. Can this contractor meet your construction schedule? If the contractor goes over the specified construction schedule without your approval, are there any penalties? Are they clear in the contract? How are "change orders" to be resolved?
8. Does the contractor use "subs"? If so, for what work and who are they?
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Don Gaddes Michigan Valley Homes provides complete residential and commercial construction and remodeling services for the Ann Arbor Michigan and Jackson Michigan areas.
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