Hathmore

Whole House Diagnostics and Repair

Contractors trained in "whole house diagnostics and repair" understand the "house as a system"- the interrelationship of duct leakage, house pressure, exhaust fans, duct pressures, back drafting, equipment efficiency, insulation, ventilation, air tightness, moisture, and health and safety.

A house is not static; it is more a complex organism of parts and pressure at odds with themselves and rarely able to maintain equilibrium, driven by improperly sized and poorly installed heating and air conditioning systems inducing positive pressures in some zones and negative pressures in others while dryers, vent-a-hoods, power roof vents, Jenn-Aire ranges and bathroom vent fans actively exhaust air while furnace and water heater vent pipes and the house itself behave like chimneys drawing outside air in through penetrations in the crawlspace and the building envelope to replace conditioned air being drawn up and out through partition walls, holes in the attic, by-passes, cracks, chases and hundreds of both accidental and intentional holes and penetrations in the ceiling, walls and floor from gas pipes, electric wires, cable, telephone lines, and poorly fitting joints.

Because the house is a system, when one thing changes, something else is effected. For instance, simply plugging holes and sealing ducts can create worse problems than it fixes. Improper air sealing has resulted in fireplaces not drafting, elevated radon levels, moisture problems, and the list goes on. Why? The leaks that were sealed in the living room provided needed combustion air for the fireplace. Prior to sealing, the leaks in the basement supply duct leaks were positively pressurizing the basement and keeping radon out, but when sealed, the basement became negatively pressurized and radon and moist, contaminated crawlspace air was drawn in.

In the house-as-a system approach, there are three interdependent components that must be addressed if a house is to perform to its full potential: the BUILDING ENVELOPE, the MECHANICAL SYSTEMS and the OCCUPANT.

In addressing the "building envelope," it is important to first define where the air barrier will separate the "conditioned" and the "unconditioned" spaces. This (hopefully) continuous air barrier is typically defined by walls, ceiling, floor, doors and widows, but the unique geometry of many buildings can make defining the envelope more complex.

Second are the mechanical systems which include furnaces, air conditioners, water heaters, vents, fans, blowers, clothes dryers and any other mechanical device that moves air and induces pressures within the house.

Third is the occupant who closes doors, opens windows, sets the thermostat, changes (or fails to change) furnace filters, and in dozens of ways unknowingly prevents the building from performing at peak efficiency.

In whole house repair, "whole house" diagnostic energy inspectors and qualified contractors usually address air sealing and insulating the building envelope first, then the mechanical systems and finally the occupant. There are exceptions. If a furnace has a cracked heat exchanger, or the house has unvented gas heaters, these things should be addressed prior to sealing a house. The furnace should be repaired or replaced and the unvented gas heaters should be removed. Health and safety are always the first concerns of a truly "qualified" contractor.

Qualified contractors use diagnostic tools like blower doors, digital pressure gauges, pressure pans, Monoxers®, and Duct Blasters® for diagnosing, repairing, and pressure balancing a home.

These contractors are able to measure and pinpoint air leakage in the ducts and the building envelope before and after improvements. This allows them to know what and where the problems are, formulate a plan of action, set targets, know when the targets have been met, and test their way out of a house to make sure it is left safe and healthy as well as comfortable and more energy efficient.

To be listed as a "whole house" diagnostic energy inspectors or a qualified contractor , a contractor must have completed training in the classroom and in the field from a recognized training organization specializing in state-of-the-art diagnostic and retrofit procedures.

If you believe you have the experience and training to be listed as a "whole house" diagnostic energy inspector or a qualified contractor, click add me to list . If you are interested in receiving training in whole house diagnostics and repair, check out upcoming training classes.

Click here to order a diagnostic inspection.

Blower Doors

The blower door is a calibrated device built specifically to identify and measure the overall leakage of a building and the duct system. The blower door consists of a large fan which is mounted in a frame and placed in an exterior door. The blower door is used to depressurize (or pressurize in some cases) the house. Using the pressure readings and a computer, the leakage of the house and ducts can be calculated.

A Duct Blaster, a small blower door designed specifically to test ducts, can be used in new construction before the sheet rock covers the ducts. Used with pressure pans, pressure gauges, and a blower door in existing houses, the duct blaster can help determine the extent and location of hidden duct leakage.

The blower door greatly enhances our view of the whole house as a system, a complex interplay of temperatures, humidity, air movements, convection and forced-air pressures induced by the air-handler of the central duct system.

With the blower door testing, air leakage sites can be identified, the total air change rate of the house can be determined, duct leakage can be measured and located, and moisture, humidity, mold and mildew problems can be traced to their source.

If you are interested in more information on blower doors or upcoming blower door training, check out blower door manufacturers and training classes. If you are interested in blower doors

Duct Leakage

Addressing duct leakage and the pressures in a house is a critical part of whole house diagnostics and repair.

We have known for some time that improperly charged and improperly sized mechanical equipment and/or undersized return and supply ducts can reduce performance and shorten the life of heating and cooling equipment. We have only recently started to realize how huge the problem of duct leakage is and the enormous impact it has on system performance and heating and cooling costs.

While the duct system may comprise only 5% to 7% of the total surface area of the house, ducts are usually responsible for 18% to 30% of the total leakage of the house. Studies show supply and return duct leakage in Florida homes routinely triples a home's natural air exchange with the outside whenever the cooling system is operating.

A report by Proctor Engineering on the PG&E Appliance Doctor Pilot Project in Fresno, California determined a 24.4% cooling energy savings and 12% heating savings can be accomplished by a program that diagnoses and repairs duct leakage, airflow, and overcharge on residential central air conditioners.

Bruce Davis' 1992 Arkansas study funded by the Arkansas Energy Office showed an average 19% reduction in run time of gas furnaces and a 32% savings in heat pump houses from only sealing ducts!

More important, are the implications for health and safety.

It is estimated that one house in six has at least one supply duct with a major disconnection. When the blower for the central heating or cooling system turns on, it pumps conditioned air out of the house through leaking, improperly sealed or disconnected supply ducts. As air is pumped out and is unable to return, negative pressures are created in zones of the house where return air registers are located. The air lost to supply leaks must be replaced by outside air. In a tight house, the easiest path for outside replacement air may be down the chimney of the fireplace or vent stacks of water heaters and furnaces. This draws carbon monoxide and other combustion byproducts into the home environment.

These negative pressures can also draw in outside pollutants like mold and mildew from a crawl space as well as radon and other sub-soil gasses from under a slab or through the basement.

Leaky return cavities are probably the most common cause of outside air usually from the attic or crawlspace being drawn into the return ducts and pumped into the house. If there is more leakage on the return side than the supply side, this will positively pressurize the house which forces conditioned air out through cracks and holes of the building envelope where air exchange would normally not occur.

Both situations happening at once are usually happening. Positive pressures are causing exfiltration in bedrooms with closed doors while negative pressures draw outside air into the zone where the returns are starving for air.

This is why pressure balancing a home is critical for peak performance and health and safety, but it takes the right tools, good training and hands-on experience to be successful.

Clues to Problem Houses

Uncomfortable houses or rooms.

Uncomfortable houses or rooms that don't get warm enough in winter or cool enough in summer can be the result of one or a combination of things: air leakage, disconnected or improperly sized ducts, lack of insulation, improperly sized equipment, lack of pressure balancing, inadequate insulation, the list goes on. There is no one answer; all houses are different. However, a number of indicators of likely problems follow. If these are familiar, seek the advice of a "qualified contractor."

Leaky return duct(s).

Remove the return air grill in your house. It is probably located in a central hall or under a stairway. Look inside. Do you see a well-sealed and insulated duct or do you see studs and the back of sheetrock. If you see studs and sheetrock, you are looking into a building cavity being used as a duct. It is guaranteed not to be air tight. Its framing and the framing of connected walls almost certainly provide a path for outside air to be drawn into the house when the air handler turns on. There are no arrows to tell the air where to go; it will take the path of least resistance which will not all be neatly through the return air grill. If your return is an unsealed building cavity, it is guaranteed that you have a problem.

Leaking supply ducts.

On average, most building scientists agree that about one house in six has at least one supply duct with a major disconnect. As air is pumped out of leaking or disconnected supplies, the house at best becomes negatively pressurized which increases infiltration, decreases comfort, and increases costs. At worst, the return air duct which is now starving for air starts back-drafting fireplaces, gas water heaters and gas furnaces, drawing in carbon monoxide and other combustion by-products.

Single returns.

How many return air ducts does your house have? Ideally, every room should have a return duct. Some houses have a total of two; most houses have only one return for the entire house. The result is uneven temperatures, increased infiltration (and exfiltration), increased duct leakage, reduced equipment efficiency, and increased chance of backdrafting of combustion appliances.

Lack of pressure relief.

For a house to operate at its best, all pressure zones in the house should be balanced. The problem can come when a room, or block of rooms like a bedroom at night is closed off. If the heating or cooling unit is running, air is being put into the bedroom through the supply ducts, but it can't get back to the return because the door is closed. The bedroom becomes positively pressurized while the return zone starves for air.

When a house is properly pressure balanced, backdrafting of fireplaces, gas water heaters and gas furnaces will not occur. When doors or closed within the house, rooms will not become either negatively or positively pressurized. All rooms will get the amount of air they need to ensure comfort and even temperatures throughout the house.

Will undercutting doors relieve pressure?

Maybe, but look at a master bedroom with a large bathroom and walk-in closet. Add up the total square inches of the maybe four to six registers and see how many inches you would have to undercut the door for equivalent square inches and adequate pressure relief. The result wouldn't allow for much privacy! Yet, there are a dozen ways to relieve pressure in a room that are rarely used.

Fireplace won't draft.

A fireplace that won't draft could be the result of several things. It could be simply poor design with not enough height in the chimney or a poor ratio of fireplace opening to chimney area. It could be obstructions. Squirrel nests, bird nests and dead animals can all stop a fireplace from drafting.

If the chimney is unobstructed and at least 16 feet tall, opening a window in the room can provide combustion air and relieve the negative pressure. If the fireplace now drafts, you have treated the symptom, but you really haven't solved the problem. The problem is worse.

Close the window you just opened. Now turn on the clothes dryer and all the vent vans. Close all doors except those between the fireplace and the rooms with the vent fans and clothes dryer. Will the fireplace draft now? How far must you open the window in the room with the fireplace now to relieve the pressure? In a leaky, old house, probably not much. But in a reasonably tight house,open it all the way and the fireplace may still not draft.

Maybe the chimney works ok when you have a roaring fire, but what if it is late at night and you close off the kids room and go to bed and let the fire die out. A fire can start to backdraft as the fire dies down and can no longer maintain draft. If the central heating system turns on, there is now the possibility carbon monoxide will be distributed throughout the house.

This is not as uncommon as one might think. As we build tighter and tighter houses with combustion appliances located inside and disregard the pressures that are induced by mechanical systems and the "stack effect" of the house itself, we will continue to see more and more problems with carbon monoxide, indoor air quality and health and safety.

With fireplaces or any other combustion appliance, if you must have it inside the conditioned space, start by providing it with outside combustion air.

Ducts in the attic or crawlspace.

Where are your ducts? In the attic? The crawlspace? Between floors? Where should they be? Heat moves in only one direction, from hot to cold. And the greater the difference in temperature, the faster it moves.

The attic is the worst location for ducts. The attic is the same temperature as the cold outside in the winter. In the summer its worse, the attic is much hotter than outside. Trying to deliver 70 degree air through a duct located in a 140 degree attic is like trying to wash your car with a soaker hose- there may be a trickle of water coming out the end, but much of it was lost along the way.

The crawlspace is better than the attic for ducts. The basement is better yet. Furred down into the living space is best of all locations. If your ducts are furred down into the living space, any cooling or heating loss is lost to the conditioned space, so it is really not "lost."

Flex duct.

If you have flex duct snaking around in the attic or under the floor, it is a sign of a low-ball bid job. Flex duct is easily collapsed. The spiral wire which gives it its shape creates added friction inside and slows down air movement. It is typically underinsulated. If it has vinyl outer cover and is exposed to sunlight, will break down and fall apart.

Duct tape.

Called temporary tape, duct tape is a problem, particularly in areas like a damp crawlspace or an attic where temperatures fluctuate. The one place to not use duct tape is on ducts! Mastic is better. It goes on like mashed potatoes, sets up and stops leaks for the life of the system.

Fiberglass ceiling insulation.

Fiberglass does not stop air movement; that is why it is used for filters. If you see dirty spots around fiberglass insulation on ducts, in an attic or under the floor, it indicates a place where the fiberglass has filtered and trapped the dirt as air has passed through. Unless all penetrations in the attic floor were first carefully sealed, blown fiberglass insulation in the attic does not necessarily mean you have a well-insulated attic.

There are some new blown fiberglass insulation products with binders coming into the market that have properties for stopping air leakage similar to cellulose. Fiberglass batts, if carefully installed, can do a better job of stopping air leaks in the attic than loose blown fiberglass.

The key words are "carefully installed." Be sure to carefully fit batts around wiring and plumbing. In addition, they should be cross-linked in the attic, that is, batts should be laid between the joist until they are higher than the joists, and the next layer should be laid in the opposite direction. If you are adding additional insulation over fiberglass batts, consider blowing cellulose for higher R-value and reduced air leakage.

Hiring a Contractor

In screening contractors, the following are some questions you may want to ask:

Do you build energy efficient houses?

Most all builders say yes, but make sure. Ask for references. Agree on the specifications for the home before you start, including pressure relief in all rooms and air tightness of the building envelope and the duct system. It will depend on the size and location of the house and the number of occupants, but you will want to spec the finished house in the range of 3.5-.4 natural air changes per hour.

Get your contractor to agree to have the ducts tested for air leakage prior to the sheetrock covering them up. Get any combustion appliances like a gas water heater or gas furnace outside the building envelope. If they have to be located inside, supply adequate outside combustion air, insulate the closet walls and use an airtight, insulated door to the closet. When completed, have the house blower door tested to ensure health and safety, comfort and maximum energy efficiency.

How energy efficient do you build?

"Energy efficient" for an energy efficient mortgage means the house meets the Model Energy Code (MEC). But remember, not all state have adopted MEC. Most builders build to code, and while that may sound good, what it also means is that the house is the least efficient allowed by law.

Get a home energy rating on the plans before you start. You will want a house that exceeds the "minimum allowed by law." Try for an energy rating of FIVE STAR and at least FOUR STAR PLUS for a new home, and THREE PLUS to FOUR STAR if you are upgrading an existing home. See ordering an energy rating.

Are you a member of the Energy Efficient Building Association?

The Energy Efficient Building Association (EEBA) is a national organization of builders and trade allies who specialize in energy efficient construction that usually exceeds the minimum standards of CABO/MEC. Membership in EEBA is a good indicator of an exceptional builder.

EEBA is a leading provider of builder training in the area of resource efficient design of homes and small commercial buildings. Founded in 1981; now with over 500 members, EEBA works internationally to reduce energy waste, improve resource efficiency and help the environment through better builder training and direct member services.

Located in Minnesota, with a service bureau in Washington, DC, EEBA can assist most home builders, remodelers or designers to produce more resource efficient low-energy buildings that are healthy, comfortable, durable, have excellent resale value, and help maintain environmental quality.

Can you explain the concept of a "house as a system?"

Review "whole house" diagnostics and repair on this site and judge your contractor's answer for yourself.

How tight should my house be?

A natural air change rate of .35 to. 4 natural air changes per hour (nach) is usually ideal for comfort and air quality, but it will vary with the size of the house and the number of occupants. Remember, you will not know for sure how tight your house is without measuring it!

How do you measure the tightness of a house?

Blower door is the right answer, but "tracer gas" would gets high marks.

From the return grill to the supply registers, what is the maximum leakage you can guarantee my ducts to be when you are finished?

There should be NO leakage, but there will almost always be some because of the way equipment is manufactured. For new installations, aim for a maximum of 50cfm25 (that means 50 cubic feet of leakage per minute at 25 Pascals of pressure). For retrofit,75 to 100 cfm25 is pretty good.

How will you measure that?

A Duct Blaster or a blower door are both good answers.

What is a Pascal?

A Pascal is a unit for measuring pressure. 50 Pascals is about the same as .5 inches of water column (heating and air conditioning talk).

What kind of insulation should I have blown into the walls of my old house built with no insulation?

Cellulose is preferable fro blowing side walls. It not only has higher R-value than fiberglass or rock wool, but it stops air leaks.

What about walls of my new house?

Wet spray cellulose is hard to beat. Same reasons as above, plus no voids in the wall from wiring, plumbing, etc. However, some of the new wet-blown fiberglass insulation products have similar properties to wet-blown cellulose. Some foams may also be acceptable, but are usually cost-prohibitive. Use fiberglass or rock wool batts only if all penetrations in the wall cavities are carefully sealed and a house wrap or exterior insulation sheathing is installed to further ensure air leakage reduction as the house moves over time. If you use wet-blown cellulose, a house wrap is unnecessary.

How about insulation under my floor?

Fiberglass batts under the floor are acceptable after sealing all penetrations, holes, openings, etc. Or, insulate the perimeter sidewalls with rigid insulation or wet blown cellulose and add a polyethylene ground cover to keep out moisture.

How will my air conditioner be sized?

Use a Manual J calculation or equivalent. WRONG ANSWERS include: "One ton per 500 square feet like dad used to" or "I've done enough houses to eye-ball it." Don't assume you can simply replace it with the same size as what's there. The existing one may not have been sized correctly to begin with, and/or some things may have changed since it was installed.

In doing your sizing calculation, what is the natural air exchange rate you will use?

Determining the air leakage of a home is a guess unless the house is tested (like with a blower door). Most new houses average .5 to .6 natural air changes per hour (nach). Older homes range from around one to two and sometimes three; they vary a lot.

For adding or replacing equipment in an older home, here's the rub. If you install an air conditioner in a leaky uninsulated home it will have to be huge. The next year, if you insulate and air seal, the unit will then be oversized and won't run long enough to remove moisture. The result is high humidity and discomfort. Always air seal and insulate first and then size equipment!

Do you duct tape all your joints?

If the contractor says "Of course!" it's the wrong answer. Duct tape may still be the industry standard, but duct mastic is way better. It goes on like mashed potatoes and it lasts. If the contractor says no, we don't use duct tape, we use mastic, hire 'em! But check the work before you pay. Peel back the insulation hiding several joints and make sure they really did!

Remember, you don't get what you expect, you get what you inspect!

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