Take the ENERGY STAR new homes program, for example, the one I’m most familiar with. Version 1 required only one inspection, a home energy rating (for the performance path), and no checklists. Version 3, which becomes mandatory for builders wanting the ENERGY STAR label on their homes starting next January, requires 2 inspections, a home energy rating, and 4 checklists.

I understand the need for it from the perspective of the program administrators. Building and energy codes are catching up with voluntary program requirements, so they have to keep moving forward. Program leaders also have attempted to clarify the ambiguity of early versions of program requirements. And they have to make sure that the program is meaningful and that when the program label appears on a home, that home is significantly better than homes without the label. I get all that.

It just seems like we’ve lost our way, that we’ve all gotten blinded by a confusion of checklists, worksheets, prescriptive measures, and certification levels. Not to mention the confusion that comes from having so many different programs out there. If you’re a builder, you have to decide if you’re going for ENERGY STAR, LEED for Homes, EarthCraft House, NAHB Green Building Standard, Environments for Living… It’s not an easy task.

One of the first points of confusion that participants in the ENERGY STAR program face is whether to certify via the prescriptive or the performance path. That sounds pretty clear-cut, right? When you take a closer look, however, you find that the prescriptive path has performance requirements (e.g., testing for duct leakage and infiltration rates), and the performance path is chock full of prescriptive requirements. Just look at the 4 checklists required in ENERGY STAR Version 3.

As constructed, the performance path is differentiated from the prescriptive path by its requirement for a HERS rating. It’s based on how the home is constructed, how it tests out, and how the software does the energy modeling. It doesn’t depend on how the house actually performs, though, and that could differ significantly from the modeled performance. One reason we do it this way is so that the homes certified will carry the program label while they’re for sale, thus helping the builder to market their homes.

But what if we included the performance of a home over its first year of occupancy? Then we could include the actual energy use and calculate the energy intensity, even separating out baseload from the energy used for heating and cooling. It seems to me that this would be one of the best ways to handle quality assurance, too. If HERS raters, builders, and trade contractors know that their work has to pass not only the initial inspections but also a full year’s worth of performance assessments, don’t you think they’ll pay a bit more attention to getting the details right?

We could simplify the requirements for the initial certification and make sure everyone knows that the initial label means only that the home has gone through a process. Even though the energy modeling may say the home will use only $900 of energy per year, for example, everyone will know that that will be compared to the actual energy consumption for the ‘real’ label.

Anyway, those are my thoughts on this Monday morning. I’m interested to hear what you think.

Top photo by acearchie from flickr.com, used under a Creative Commons license. Lower photo by Ian Sane from flickr.com, used under a Creative Commons license.

Yesterday, though, I received a Manual J to go along with a file for an ENERGY STAR home that was beyond the pale. It was egregiously horrific. It was spectacularly sordid. It did come close to meeting the ENERGY STAR Version 2 requirements for Manual J (tight or semi-tight infiltration and correct design temperatures), but whoever put this one together was singularly devious in his efforts to justify the oversized air conditioning systems he wanted to install.

Yeah, he did the usual things to fabricate extra cooling load, but when that wasn’t enough, he resorted to one trick that’s not used nearly as often as it might be. Keep reading, my friend, and I’ll let you in on his secret.

One of the first things I do when checking to see if a cooling system might be oversized is to look at the ratio of conditioned floor area (in square feet) to the cooling capacity (in tons). ENERGY STAR and other high performance homes usually come in at about 1000 square feet per ton or more. The house I builtwas about 2000 square feet per ton.

A lot of HVAC contractors, though, don’t do Manual J sizing calculations but instead rely on rules of thumb. Mostly they use 500 to 600 square feet per ton. This house came in at 368 square feet per ton! That’s ridiculous, especially for a house in Charlotte, NC.

When I went into the reports, here are the problems I found that are typical of bad Manual J’s:

• They put 6 people in the calculation when this house should have had 4. (It should be the number of bedrooms plus one.)
• The HERS rater calculated that the house had 184 square feet of window area; the Manual J had 383 sf.
• The HERS rater used a window U-value of 0.32; the Manual J had 0.53. (Lower is better.)

Those three items alone inflated the cooling load sigificantly. Not enough for this contractor, though. Evidently he really wanted to install a 2.5 ton air conditioner for the upstairs zone, yet after all those shenanigans, the Manual J result was only 1.5 tons. So, what did he do to get that extra ton to show up in the Manual J? He could have gone in changed wall insulation or duct leakage or any number of other parameters, but there was an easier way.

Manual J calculates the sensible and latent loads separately and adds them together for the total load in Btu/hour. The sensible load is how much cooling you need to do to bring the temperature down, and the latent load is how much cooling you have to do to bring the humidity down. If you take the sensible load and divide it by the total load (stick with me here – we’re almost there), you get what’s called the Sensible Heat Ratio, or SHR.

The Manual J report often submitted shows the total load (sensible plus latent), but it also shows what they call the required total capacity of the equipment at a particular SHR. Whoever does the Manual J can override the default SHR of 0.75, and that changes the required capacity. Most air conditioning equipment comes with an SHR in the 0.7 to 0.75 range.

The crafty calculator who completed this Manual J figured out that by adusting the SHR, he could get the required capacity to equal what he wanted to install. In this case, he needed 0.53 SHR to get his 2.5 tons. Can you even get an air conditioner with 0.53 SHR?

Come on, HVAC guys! Do it right! If you can’t do this for ENERGY STAR Version 2, you don’t have a chance with ENERGY STAR Version 3, which is much harder.

To heat and cool a home built for high performance, a professional builder can select top-quality heating and cooling equipment to ensure year-round comfort and energy savings. However, if the owners want that equipment to perform as designed, they must maintain it.

Fortunately, the proper maintenance of heating, ventilating, and air conditioning systems (commonly referred to as “HVAC”) does not require homeowners to be mechanical contractors. A few easy steps for preventive care, conducted on schedule, are usually all it takes to keep those systems humming at peak performance.

The vast majority of residential HVAC systems are “forced air” configurations. The system consists of a centrally located condenser along with a furnace and blower units that push heated or cooled air through a network of large pipes (or ducts) into the rooms of the house through vent registers.

A forced air system relies on other ducts to suck in and return air to the system from registers near the ceiling. “Return” air is either recycled through the system or exhausted to the outside, keeping the inside air fresh and comfortable.

Maintaining this system starts at the blower, which circulates a high volume of air. The blower contains a removable filter to prevent small particles and allergens from contaminating the indoor air. For most HVAC systems, the filter should be replaced every three months. Some newer, high-performance systems may have filters that only need to be replaced semi-annually or even just once a year. Consult your owner’s manual for frequency of replacement as well as size of filter. Filters of all sizes are available at most home improvement and hardware stores and are easy to remove and reinsert into the blower.

The next component to maintain is the ductwork. It’s a good idea, even in a new house, to have the ducts cleaned out at least every two years. In fact, most professional builders will offer or simply conduct a thorough duct cleaning before the owners of a new house take occupancy. Responsible builders do not want their buyers to be greeted with a puff of construction dust the first time the HVAC system is used! Two years later, the owners should contact a local duct-cleaning service or ask their builder for a recommendation.

On the same every-other-year schedule, the entire HVAC system should be checked by a professional mechanical contractor. Again, your builder can recommend a reputable service, ideally the company that installed the system. This check-up will ensure that the system is operating properly; bringing enough fresh air into the house, providing adequate ventilation and maximizing energy efficiency. Homeowners can do random spot checks by inspecting the outside of the equipment for any leaks, cracks, or other abnormalities and reporting those to their builder or HVAC service contractor.

This type of simple and inexpensive maintenance program will help to keep the HVAC system running at optimum performance for many years.

There is a direct connection between heat loss and heat gain as it relates to your home’s protective skin, also known as the building envelope. Ideally your home should maximize heat retention during the winter and minimize heat gain during the summer. The best energy efficient design should incorporate a well sealed and insulated wall structure that helps protect you from temperature change and block unwanted moisture and air from entering your home. These mechanisms are known as transmission and air leakage.

Thermal resistance (your home’s wall insulation) and surface area are two factors that govern the rate of heat transmission. Air leakage is measured in CFM (cubic feet per minute) and depends on the surface area of the holes in your home and the pressure differences between the outside and inside. A large difference in temperature, known as ∆T (Delta “T”), creates a greater pressure. Maintaining a balanced interior pressure will improve indoor air quality. Sealing or reducing the number of air leaks in your home not only stops unwanted air infiltration (both cold or warm air) but also lowers the amount of moisture that rides along the air flow path and helps maintain pressure balance.

A second source of pressure change occurs when air leaks in through the building skin as a result of your home’s air conditioner. Air leakage into your home is often 2-3 times greater when the air handler (your air conditioners’ fan motor) is operating. The unit “de-pressurizes” your home and increases the opportunity for air infiltration. Stopping the holes will lower the pressure difference.

A third, and often overlooked, pressure change can occur as a result of leaky ducts in either the supply or the return air chamber of your heating system. This type of unbalanced system can also create a depressurized “combustion appliance zone” (CAZ). An example would be a back drafting chimney (and its accompanying odor) or a flame roll-out of the water heater. Both have been known to cause house fires. Also, if you’ve noticed that as you shut a bedroom door the last few inches the door is “sucked shut”, you should have a balance test performed on your heating system. These “out of balance” pressure zones can create unhealthy conditions by pulling unwanted air from a water heater exhaust (can create dangerous level of carbon monoxide) or an increased level of soil gases (radon).

Maintain your home by regularly checking for and repairing air leaks to your heating system and your home’s skin. Doing so will help keep your family healthy and lower your energy bills at the same time.

Listen to How Air Affects a House

This podcast series is excerpted from a two-day class called “Building Science Fundamentals” taught by Dr. Joe Lstiburek and Dr. John Straube, of Building Science Corporation.

What is 2 to 1000 times greater inside than out, is impossible to see but at the same time has the potential to damage your eyes, can cause dizziness and nausea, and vaporizes at normal temperature and atmosphere? You guessed it…VOCs or volatile organic compounds.

Many of us spend more than 90% of our time indoors. Clean indoor air is as important as breathing. Some of the most critical factors influencing indoor air pollution concern our ability to eliminate or reduce specific sources such as tobacco smoke, radon, chemical irritants, and pesticides. It’s also as important that you control moisture, which can lead to mold growth and bacteria.

Ideally, it would be best to prevent these pollutants from being released in the first place, but that is not always possible or practical. An increased focus on proper ventilation can play a critical role in determining whether our indoor environment is healthy or not.

As a green building verifier my role is to help eliminate these conditions by teaching practical and proper building practices.

Listen to this National Public Radio program (Windows Media Player) conducted at Syracuse University on indoor air quality.

To learn more about VOCs and how to eliminate poor indoor air quality during construction contact Gary N Smith toll free at 877.809.6139 or visit him online at http://www.garynsmith.net.