Airtight Window Installation

A very common complaint we hear from homeowners is that of leaky windows. We tend to think of windows as holes in the wall and therefore the source of all the leaks in a house.

From the use of advanced diagnostic equipment such as blower doors and infrared scanners, we know that windows are rarely a major contributor to an air leakage problem. However, even small window leaks can be a problem to someone who is sitting next to such a window.

All window manufacturers must meet Federal standards for air leakage. There are certainly windows that are less leaky than others, but no brand of window is excessively leaky. The only area of window leakage that is not controlled in a factory is the installation, and in fact many window problems we find are due to improper installation.

Most windows have a nailing flange, and manufacturers installations instructions usually call for caulking of the flange to the exterior sheathing. In fact this is a very important step and it is necessary that your installer understand what is required.

The idea is that a continuous bead of caulk is installed around the window where it joins the house so that there is no possibility of air getting around the window flange and into the wall.

The caulk bead should first be applied to the window flanges just before installation, then after the window is installed, it should be touched up to make sure that it is continuous on the sides, at the corners, and along sills that may not have flanges.

If the window has no flanges, then caulking should be applied under brick molding or other members to again complete the continuous bead of caulk completely around the window.

Alternatively, a good grade of tape such as 3-M or Venture red tape, or the new Tyvek tape can be used at the flange, as long as they are installed so that they are continuous.

Manufacturers do not want foam installed around the interior frame-to-rough-opening joint because, despite careful installation, there is a good chance the foam will expand and distort the window frame. A proper caulk bead at installation will do the same job with no danger of distortion.

Mysterious Carpet Sooting

Over the last four or five years we have been asked to investigate a growing number of carpet sooting problems. Carpet sooting is distinct from carpet soiling - carpet soiling is dirt under doors or around room edges that can be removed using conventional carpet cleaning techniques. However, carpet sooting is actual black, greasy soot in these and other locations, and it cannot be cleaned completely. In fact it is not covered under "Stainmaster" type carpet warranties!

We have seen this problem in one story houses on slab and four story houses with basements, oil, gas, and propane heated houses and heat pump heated houses, houses with fireplaces and houses without, houses with attached garages and houses with no garages, builder's sample homes heated for two years but with no problem until 3 months after occupancy, and middle of row townhouses with no problems on either side.

First let me state what carpet sooting is PROBABLY NOT: it is probably not by-products of combustion from a heater, water heater, or gas range; it is not a backdrafting heater; it is not faulty ductwork; it is not excessive house tightness or excessive house leakiness. We see no consistency with these potential causes and carpet sooting, however, it is important to check some of them out to be sure they can be eliminated as sooting sources.

It is simple to say what this problem is not, but not so simple to say what this problem is. We have seen half a dozen "expert" explanations, each of which we could dispute with field experience. However, the problem is currently being researched by the NAHB and many independents, and we are starting to see patterns in their results.

It now appears that in order to have the sooting problem you have to have two things: soot production, even small amounts, and a mechanism that forces that soot to become deposited.

Possible sources of soot production are faulty heaters, unvented fireplaces or heaters, a gas range or oven, candle burning, or any other open flame.

Some of the ways that soot is forced to deposit are electrical charging, warm air/cold surface attraction, and high velocity air streams.

Electrical charging happens when very small soot particles make their way through the furnace filter and become charged in the duct system by high air speed coupled with either a rough duct interior or an obstruction - these conditions give a small electrical charge which makes the soot particle want to stick to some surfaces. It can also happen with certain plastics that you may have noted had a static charge, such as the interior of a refrigerator. Warm air/cold surface attraction happens when warm, soot laden air rises against and a cooler surface and the soot is attracted to that cool surface. And high velocity air streams can deposit soot at floor grills or on adjacent walls.

These are only some of the reasons that the soot is deposited in a certain area. You can also find a build-up along some (not all) baseboards, under some (not all) doors, on counter tops, in (yes "in") kitchen cabinets behind closed doors, in (yes "in") refrigerators behind closed doors, and on most horizontal surfaces.

What the research is pointing to is this: Candle burning is the most frequent cause of carpet sooting. Candle purchasing is at an all time high (more than the "flower power" late 60's!), there are more soot producing, petroleum based aromatic oils added to candles, paraffin formulation has changed recently to include greater percentages of oil products which produce more soot, and white and other light colored carpeting has come into fashion.

A recent visit to a popular chain importer revealed that every candle had "instructions" that told the user to 1) trim the wick to 1/4", 2) avoid drafts, and 3) limit burn time, usually to 3-4 hours. Each of these practices reduces soot production. An employee of that store said "of course you have to trim the wick or it gets that black stuff all over your walls". It would seem that candle manufacturers are starting to recognize potential problems from their products. By the way, I know no one who trims candle wicks!

Candle burning, then, appears to be the main culprit, and was the cause of 27 out of 28 cases in a recent Florida study (the 28th case was questionably candles). We have certainly seen cases where there were no candles involved, but this explanation goes a long way toward solving many of the cases that we have seen. Most home owners insurance policies will cover repairs due to candle burning, but only the first time it happens.

The complete explanation to this sooting problem is still being worked out. Unvented fireplaces have been the cause, and we never recommend their installation for this and other reasons. We are learning daily and will know more in the near future. Please feel free to call to discuss this problem at any time and we will share what we have learned.

The Room Over The Garage

The most frequent complaint we deal with is a problem in an occupied room over garage. Heating or air conditioning this type of room takes special consideration. There are four different causes of comfort problems associated with this type of room:

First is the increased exterior wall surface ratio - in other words there maybe five of the six room surfaces exposed to the exterior. Your dining room may have one exterior wall as the only exposure to the outside, but your room over the garage can have three walls, a floor and a ceiling with outside temperatures on the other side - this means very high conductive losses. R-Value is the only way to stop conducted heat loss, so it is important that the full specified insulation thickness be installed in walls and ceilings. Floors (garage ceilings) are typically specified at R-19, but we recommend filling the cavity even if it takes R-38 or more to do so. Improper installation of insulation is common and results in getting only a fraction of the stated R-Value in this area. Proper installation means that the insulation must touch the surface it is insulating: in the walls, the insulation must touch the back of the drywall; in the ceiling, it also must touch the back of the drywall; in the garage ceiling, however, it must touch the bottom of the plywood floor deck of the room above. We also strongly recommend that any plumbing pipes and ductwork be installed so that they, too, touch the bottom of the plywood floor deck so that they have the full benefit of the insulation below them. Remember that no amount of insulation will bring the floor of these rooms up to the same temperature as the air in the room. Carpeting helps because it insulates your foot, however, tile bathrooms are bad because your feet are wet and the cool floor is much more apparent even though it is the same temperature as the carpet.

The second problem is air leakage. There is more potential for leakage in a room over a garage than in other rooms in the house, and also, since these rooms are generally cooler, the leakage that is there is more apparent. Proper tightening technique would include checking band joists, knee walls, duct soffitts in garage ceilings, block/drywall joints in garage, lolly columns and other penetrations of the garage ceiling, as well as general tightening.

The third problem is HVAC supply. We frequently find these rooms undersupplied because the increased heat loss has not been accounted for. We recommend that a separate heat loss calculation be performed on the room, the appropriate air flow be supplied, and all joints in this area taped. We have never seen one of these rooms with too much heat!

Your HVAC installer should also take into account that these are usually the longest ducts in the house, and that they pass through the colder space between garage ceiling and room floor, or, in a worst case, through the attic. This means that these ducts deliver a lower flow with cooler air, reducing the BTU's delivered to the room.

The last problem is what we call a "sensing" problem. This room has increased heat loss, possibly more infiltration, the air supply is slower due to duct length, and that air supply is also cooler due to the colder space that the duct must travel through. So we have a room that does cools off quicker and heats up more slowly. The thermostat is located inside the main body of the house and is "sensing" the temperature changes in, say, the dining room. The dining room, however, has an average amount of heat supply and an average amount of heat loss. If the thermostat is calling for the furnace for ten minutes on and ten minutes off, that is enough for the dining room, but the over garage room is cooling off too fast to respond to the heating cycle. The thermostat is not "sensing" the temperature in the cold room. In extreme cases, the solution is to supply a separate system that can "sense" the temperature swings in the cold room. This could be as simple as a small strip heater with its own thermostat or as complex as a motorized splitter damper on a thermostat in the cold room.

Every room over a garage should be carefully insulated and sealed, and we recommend a separate heat loss calculation on each one to determine the proper BTU delivery. However, there are no clear cut rules as to when to supply a separate thermostat. A room that bumps five feet out over a garage might not need even increased supply, but a tile bathroom completely over a garage would almost definitely need auxiliary heat.

Insulation: The Rest of The Story

Insulation is installed in walls and ceilings to slow down the flow of heat between the interior and exterior of the house. "R-Value" is the term used to measure a material's insulating value. The higher the "R", the higher the resistance to heat, and therefore the better the insulation.

Each time the R-Value is doubled the heat loss is cut in half. Doubling R-1 to R-2 cuts the heat loss in half, but so does doubling R-20 to R-40. It costs much less to bring R-1 to R-2 than to bring R-20 to R-40, and going from R-1 to R-2 saves much more energy. Depending on the cost per "R", a point is reached were your investment in increased insulation will never be returned. You can readily see the diminishing returns for heaping on more and more insulation. Insulation recommendations are made with this cost/benefit calculation in mind.

The amount of insulation that you will install is only one concern. The material that you install is an equally important decision. Fiberglass, both blown and batts, cellulose, and mineral wool all have approximately the same R-Value per inch: about R-3 to 3.5. Energy sheathing has an R-Value of about 6 an inch. Drywall, sheathing, and framing lumber all have an R-value of about 1 per inch. Fiberglass and mineral wool tend to allow air convection in their fibers to degrade their "R" value, while cellulose is much more solid and resists that movement. Energy sheathing, while expensive, allows no internal air convection and therefore contributes more to the over all quality of the wall. The factors that would recommend one material over another are: ease of installation, durability, cost per installed R-Value, and the ability to cut down on convective air movement.

We try to increase effective R-Value without spending too much money to justify our decision. In a wall, the reasonable possibilities range from a 2X4 wall with R-13 batt and OSB sheathing at R-15 total to a 2X6 wall with an R-22 batt and an inch of energy sheathing at R-31 total. However, taking into account the factors mentioned above, we recommend a 2X4 wall with an R-13 batt and 1" of energy board for an R-22 total. This is an excellent compromise between cost and benefit, and only requires a1/2" jamb extension on windows and doors.

Improperly insulating an attic can reduce its effective R-Value by 1/3 or more. Batts do not sit down tightly on the drywall where they are pushed up by wires, fans, lights, framing members, or poor installation, and at the edges of each batt where their tab is folded over for stapling. In addition, with batts there is no insulation on top of the joists on the attic floor, leaving these areas radically under insulated when compared to the R-30 of the batt. The overall R-Value in a batted attic may be as low as R-18. Blown insulation solves these problems by contacting the drywall, working in around the wires and fans, and by covering the joists with an additional layer of insulation. The R-30 blown attic will be much closer to R-30, plus its cheaper to boot. We recommend blown cellulose in attics.

Cathedral ceilings are a trouble spot in that the rafter thickness is rarely the 10 inches needed for an R-30 batt to be installed. A solution that we like for 2X6 and 2X8 rafters is to install an R-19 batt and then an inch of energy board on the inside, under the drywall. This gives an R-25 ceiling without incurring expense for packing out the entire ceiling. An insulation "baffle" or air channel must be installed above the batt, against the roof sheathing, to allow for ventilation. In addition, we recommend stapling the paper face of the batt to the top plate of the wall at the bottom of the cathedral to prevent ventilation air from rushing up between the back of the drywall and the face of the batt.

Economics dictate that if you have the space, you install all the insulation that will fit. So in overhangs, cantilevers, and areas like garage ceilings, we always recommend filling the cavity with insulation. In cases like this, be sure that the insulation is physically touching the surface that you intend to insulate - that is, the floor sheathing above the garage, and the band and soffit in an overhang. Also be sure that all of the water pipes and air ducts in these areas are as close to the heated surface as possible.

Any wall that is exposed to an attic on one side, such as knee walls or walls that back on an attic over a garage, must be given careful attention. If we only batt these walls the same as the other exterior walls, then they do not get the benefit of the added R-Value of the sheathing, and their insulation becomes exposed to degradation due to air movement on their backsides. We also frequently see batts that have fallen into the attic because they are not well fastened. We recommend sheathing the attic side of all exposed walls to boost the R-Value to match that of the other exterior walls, to keep the batts in place over the long run, and to keep air movement out of the back of the batt. Energy board is inexpensive and easy to install in these areas.

When insulating, always remember the rule that the insulation must physically touch the location of the energy loss. This is the drywall of walls, kneewalls, and ceilings, and the floor sheathing of rooms over garages.

Ductwork Basics

Ducts are a critical part of your heating and cooling delivery system, yet they are given very little emphasis during construction. We encounter many systems with 92% efficient furnaces and 50% efficient duct systems. In order to have a duct system that performs properly, there are a few do's and don'ts that must be understood:

Duct Sizing:
In order to arrive at the proper duct size, a heat loss calculation must be done on every house, or every model in a development. In addition, every "problem room" must have its own calculation done to ensure proper delivery. Problem rooms would include rooms, especially bathrooms, over garages, Cape Cod style knee wall rooms, rooms with high ceilings, rooms built over a vented crawlspace, or any room configuration that could result in high exposure to the elements. It doesn't hurt to slightly oversize ducts to problem areas.

Duct Location:
The ductwork carries the hottest air in the house in the winter, and the coldest air in the house in the summer. In other words, these ducts carry the most expensive air in the house. We typically insulate our attics to R-30 to protect our 70-75° house from a hot or cold attic. However, we only insulate attic ducts to R-6 to protect the most expensive air in the house from these same attic temperatures. The best solution to this problem is to keep the ducts out of the attic, but if a short attic run is essential, this run should be low on the attic floor, between two joists, with R-30 insulation installed over the duct after sealing all joints and seams with a high quality sealant.

The heating/cooling unit itself is very lightly insulated, and leaks a lot of air. These units should definitely be inside the house.

Remember that a basement is a semi-conditioned space, and that it rarely will drop below 62-64°. If you need two systems in a large house, then consider putting both systems in the basement, one heating the left half of the house and the other heating the right half of the house. If you have to put a system in the upper half of the house, consider putting the unit in a closet to minimize exposure to the attic, and then putting a minimum of ductwork in the attic.

In situations where ductwork must be located in an exterior cavity such as the ceiling of a garage or an exterior wall, the duct should be rectangular or oval, and should make physical contact with the interior, heated surface. This way the maximum amount of insulation can be installed on the cold side of the duct keeping it as warm as possible (this same technique is best for water pipes to prevent freezing). Be aware of energy codes when insulating these cavities.

Remember also that returns are an important part of the ductwork and that the temperature of the return air influences the temperature of the supply air. With this in mind, be sure that no returns are run through an attic without being thoroughly sealed and heavily insulated, and that no returns are run through a garage ceiling or exterior wall without allowing for space for insulation, again keeping the appropriate energy codes in mind. Best to keep them inside!

Duct Leakage:
Ductwork is designed to deliver air from one location to another. If supplies or returns are leaking, then this air is not going where it is intended to go. With this in mind, there are areas of ductwork that must be sealed to prevent waste of conditioned air.

Returns should be sealed from the grill to the air handler. Every degree that the return air temperature drops due to outside air being sucked in is a corresponding degree that the supply air drops, potentially causing comfort complaints and high bill problems. Problems here can range from small cracks to missing headers.

Ductwork in attics should be sealed as airtight as possible using high grade sealants - you don't want your sealant to fail after a couple of years. All ductwork that runs through an unconditioned space should be sealed with high quality sealant before insulation is installed.

Many supply ducts are installed inside the heated shell, and leaked supply air is contained inside of a properly sealed house. However, the larger potential leakage points should be sealed to get the air to go where you want it to.

We have seen 50 year old houses with well designed duct systems, and brand new houses with ones that are poorly designed. If you are building a new home, the changes needed are generally inexpensive and very worthwhile. If you have an older home, problems are a bit harder to solve, but solutions are still possible.

Making Your Air Conditioner Condition Air

Are you building a new home and deciding on air conditioning? Are you thinking of installing air conditioning in your current home? There are several pitfalls you should know about that can reduce the efficiency of even the best units by half, resulting in warm, humid spots and in higher bills than necessary.

The first problem to guard against is oversizing an air conditioner. On first thought, this would seem like a good idea - how can you have too much cold! There are three reasons:

First is that an air conditioner is most efficient when it has been running a while. If it is too big, it will run for a couple of minutes at a shot, whereas, if it is the right size, it will run much longer - on the hottest afternoons of the year, it should run all the time. This delivers the cold at the lowest cost.

The second is that the air conditioner is also a dehumidifier. Here in the Mid-Atlantic we spend about half of our air conditioning money on taking moisture out of the air. If the unit is too big and spends more time off than on, the coils won't get cold enough long enough to condense enough moisture.

The third problem with oversizing the air conditioner is that if you buy too big a unit, you are wasting money. A properly sized unit has a fudge factor built in, so that once a proper heat loss/gain calculation has been done buying a bigger unit than called for is unnecessary.

In addition to oversizing the unit, there are other factors that can spoil an installation.

You can't have a high efficiency system with low efficiency ducts. Ducts that run outside the thermal envelope, in attics and crawlspaces, typically have R-5 insulation installed. Compare this with your R-13 walls and R-30 attics! Any ducts that run in unconditioned spaces should be sealed tight and insulated to at least the level of the surrounding areas - R-40 would be desirable. It would be best to keep those ducts out of these unconditioned spaces to begin with.

The location of the air handler is also very critical. If the air conditioner is trying to make 55° air, but the air handler is in a 130° attic, then there will big reductions in the temperature that finally makes it into the house. Keep those air handlers out of attics and crawlspaces!

If ducts are in unconditioned spaces, duct leakage can introduce hot, humid air to the system if it is on the return side. Supply side leakage just blows expensive cold air to the outside. So sealing these duct systems as tight as possible is a very good idea. This is another reason to try to keep the ducts out of unconditioned spaces to begin with.

Cold air is harder to push to the second floor than warm air is. This is why so many houses that heat properly have uncomfortable second floors in the summer. There are a couple of low cost duct modifications that you make to be sure that the right amount of air is making it upstairs.

Just as in winter when house air leakage brings in cold dry air from the outdoors, in summer that air leakage brings in hot, humid air. This causes the unit to work harder and longer, and if this leakage has not been properly accounted for in design, it can cause great discomfort. In a very leaky home, you will be able to buy a smaller unit if you properly seal and measure the home.

Remember that the only way to get a "right sized" air conditioner is to have your installer complete a heat loss calculation on your home. In addition, an air infiltration measurement will allow him to avoid using the default rates, and therefore perhaps offer you a smaller unit. You can see how important it is to consider all aspects of your air conditioner installations. If you are installing new systems or replacing existing units, call us for details on these low-cost, no-cost considerations.

Insulating Your Basement

Homes today are much more efficient than those built even 10 years ago. Low-E glass, hi-efficiency heating and cooling equipment, and airtight construction have taken the edge off of high bills. However, one area that has not been addressed until recently is the foundation.

The Model Energy Code, and most other codes and energy programs, recognize this shortcoming and include basement insulation in their mix of standards.

Besides energy savings, this practice also results in greater comfort and less potential condensation and mold growth. Before the walls are insulated, care must be taken that moisture problems are addressed through waterproofing and drainage.

The walls can then be insulated on either the inside or outside surface. There are a number of exterior insulation systems, and they mostly involve a stucco coat over the insulation layer. It is usually a lower cost option to treat the inside of the basement walls. The most common practice locally is to use a wide, continuous insulation blanket attached to the wall. This gives good insulation values quickly and cheaply.

If the interior is to be finished, there are a couple of options. Furring strips can be added to the inside of the exterior walls and rigid foam panels installed between them. Drywall or any other interior surface can then be installed. The exterior walls can also be studded with 2 X 4's and then fiberglass batts installed before an interior finish is applied. Consider a sheet of plastic against the foundation wall to keep any moisture out of the back of the batts.

The most important thing to remember is that insulation does not work if it does not physically touch what you are trying to insulate. So any foundation insulation must be in full contact with the foundation wall.