www.energystarhomesamerica.com

Issue 10, Volume 2

October 27, 2004

What is a Heating Degree Day?
(...and why do I care?)
by Donney Dorton - Plan Department Supervisor, OKC

I remember one day last winter when it got down to freezing but warmed right back up in the afternoon sun. Wasn’t at all like the week before when the temperature dropped to 5 below and stayed in the teens all week long. What I would have given for some of that cool air last August when I wanted it the most.  How cold was it this year?  Was it colder than last year? How do we figure out how cold a year is? And is the year colder in Oklahoma City than in Dallas, is Dallas colder than Houston? Is a year colder if a record cold temperature is reached, or is a year colder if the temperature stays below a certain temperature for a month or so? Don’t we need to know how cold a year will be at the place we are building a home so that we will know how much insulation to use? The key to answering these questions is in the Heating Degree Day (HDD) calculation. 

So, what exactly is a Heating Degree Day anyway? The yearly HDD-base65 can be defined as the temperature difference between 65ºF (called the base temperature) and the average temperature (if less than 65ºF) of a particular day, with each days number added up for the year. Let’s try an example.  On January 5^th the outside temperature had a high of 30ºF and a low of 0ºF. The average temperature for that day is ((30-0)/2=15) or 15ºF. Now the difference between the base 65º and the average temperature is 50ºF (65ºF – 15ºF = 50ºF).  This represents a 50º temperature difference over one day expressed as a one-day HDD of 50.  If you add up all the daily HDD for a year you arrive at the annual HDD.  Without getting into a lot of math, we can see that a house built in a city with an annual HDD of 1000 would take twice as much energy to heat as the same house built in a city with a HDD of 500.

The most reliable HDD numbers for a particular city are determined by national reporting entities such as the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA). Some state agencies will recommend HDDs for various cities in the state.  Remember that the current HDD changes as the weather changes each day.  So when a municipality picks a certain annual HDD it must be for a specific year or maybe even an average for several years or it could be a regional average or even extrapolated from nearby cities. Most code compliance software programs assign default HDDs to specific cities. However, one city may have a different HDD in different software depending on the year and reporting agency referenced.  Some examples of a city’s HDDs are 9349 for Fargo, ND, 3742 for Oklahoma City, 2259 for Dallas, 1548 for Houston, and 607 for Brownsville, TX.

Heating Degree Days are used in the calculations of the heating loads of a house and in the calculations to determine the energy efficiency of a house. HDD is also used by the International Energy Conservation Code (IECC) to determine the minimum R-values for building components like walls, ceilings, floors and windows. It is intuitive that for heating energy efficiency we would need more insulation for a house that is in 5ºF weather for 6 months than for a house where the coldest temperature is 60ºF for only a few days per year.  Most computer programs will assign a HDD to a city and then check the R-value of the design components (walls, ceilings, windows, etc.) to see if they comply with the IECC code for that particular HDD.

OK, but how will the HDD affect me as a builder? All I need is my permit and I am good to go, right? Well, lets take a look at how the HDD day of two cities affected the code compliance. Let us use the REScheck program to determine code compliance of the same 3516sf house in two cities that are only 25 miles apart. Rescheck lists Dallas as having 2259 HDD and gave our house a score of 14.4% better than code. When we change that house to the city of Saginaw, REScheck will assign a HDD of 2625 (which has a higher code compliance) and the score drops to just 4.5% better than code. If our house had scored less than 10% better than code in Dallas it would fail code compliance in Saginaw, just 25 miles away.  What this means to builders is that more insulation or better windows will be needed in their houses built to the west of Dallas, especially if they are passing code by less than 10% in Dallas. 

While the HDD is just one number, we can see that it is a very integral part of calculating energy consumption, heating loads, and determining the IECC code.  With HDD calculations, homes can be built that meet or exceed code and are efficient and warm.  

Which reminds me of the year it got so cold that it froze sound, which is why I couldn’t hear my wife call me for supper till spring thaw.

“Live-in Lab”
by Jennifer Boyle

The House n research group of MIT and TIAX LLC have developed something called PlaceLab, a 1000sq.ft. apartment & research laboratory. PlaceLab is one apartment in a residential complex in Cambridge, Massachusetts. Volunteers agree to have their activities monitored while living there.  The primary purpose of the research is to study better ways for delivering health care in residences.  Ten million Americans over 65 are living alone today, increasing the risk for accidents.  Also, more seniors are responsible for taking medications on their own and keeping track of their own “doctor-prescribed” diets.  The built-in sensors in this apartment are designed to record eating habits and even remind individuals to take their meds. Researchers will be able to see if patients really are eating and drinking the same things they tell their doctors.  However, busting seniors for sneaking twinkies or a shot of bourbon is not the only goal of this research…

 “It is the most highly instrumented living environment ever built,” said Kent Larson, a principal research scientist at MIT. Behind the walls and cabinets are hundreds of light, temperature, humidity, water flow and other sensors. “The real challenge is to figure out what to do with all the data, so we do something useful for people.”

 “Going forward, the lab plans to host singles, couples and families of different ages for a range of academic, industry or government research projects.  Among technologies that might be tested are the microzoning of temperature for each resident of a home, light-emitting diodes that flash when the weather outside gets warm enough to open windows, or warnings that sound when older residents get down to the bottom of a staircase, where falls are most common.” says Robert Weisman of The Boston Globe.

 One feature that will be of particular interest to our readers is the monitoring of indoor air quality. PlaceLab will be used to test new air-quality monitoring systems, energy-efficient ventilation and space conditioning products, as well as advanced air treatment technologies.  The first two groups inhabited the apartment this summer, just to make sure all of the equipment was working, and the results were favorable. The actual research is set to begin soon and promises to yield highly detailed and unique results.  We’ll keep you updated.

Inspector’s Corner
By: David B. Walker – National Operations Director

“The Dirt on Dust”

If a poll were to be taken concerning the most nagging chore among homeowners, one of the top three would definitely be “dusting”. My attempt in this article is to educate you on where it comes from, and possibly, how to control it. Reducing interior dust is not hard to do, but does require an active maintenance schedule.

Where does dust emanate from? It comes from bedding, clothes, pets, indoor plants, particulates produced by cleaning products mixed with ozone particulates, vacuum cleaners – (vacuums agitate dust), dryers, and of course outdoors. Most of these are activated by a process called - “re-suspension”. This occurs through normal activity in the home that “kicks-up” tiny particulates that remain suspended in the air, and consequently remain in the air from the air movement produced by the HVAC system.

There is a greater percentage of kick-up dust found in a carpeted home, than a home with bare floors, (laminate wood, hard wood, tile). There are approximately 100-200 micrograms of dust per cubic meter held in carpets; while 5-10 micrograms are found per cubic meter on bare floors. Though these are approximates, you can see the difference between the two flooring types. Also, the amount of “traffic” within the home has much to do with an increase of these figures. However, a carpeted home will always accumulate more than a bare floor.

Most people think that the “air filter” located in the air return grill will actually serve as the “source for dust containment”. Here are a few statistics: “Media filters” remove up to 80% of particulates/dust in the “duct-work”, where only 30% is actually removed from the home.  HVAC filters can’t always catch the “kick-up” dust particulates. Even “HEPA” (high efficiency particulate air filters) will only remove 50% of indoor particulate/dust air particles. Most filters purchased today are considered “by-pass” filters. Air filters are rated for dust capture by their “MERV”, (minimum efficiency rating value); the higher the MERV, the better the particulate capture. Remember though, air filters, (by-pass filters), are in place for the particulate capture “inside” the ductwork. Most filters do a good job protecting the fan/blower, more than removing particulates from the air. One way to utilize the fan/blower for capturing particulates is to run the fan constantly – but in most climates this will not work. The energy consumption and possible humidity concerns are major factors. Filters typically work better while occupants are asleep or when the home is unoccupied. Why? Because there is a huge reduction in “kick-up” dust particulates in the air during these periods.

So, what is the solution? One way would be to slightly “pressurize” the home. This would control the ventilation rather than the home being ventilated under natural conditions. The controlled ventilation would be supplied by the HVAC system; drawn through a designed filter before being dispersed throughout the conditioned space. Controlled ventilation eliminates particulates/dust from entering through other “un-filtered” sources within the envelope. The theory of “one CFM in = one CFM out” now tells us that with the slight pressurization of the home (with clean filtered air) forces out the existing particulate/dust filled air. The pressurization of the home also reduces the chance for the home to be found under a “negative” condition. With a negative condition present, the home will begin to seek “make-up” air. These uncontrolled sources now become the vehicle for particulate/dust particles to enter the home. Combine this with the above-mentioned sources of particulate/dust it is easy to see how dust problems can exist.

Here are some other ways to reduce dust in the home. Use a vacuum cleaner with a “built-in” HEPA filter on its exhausted end. Make sure the lint-trap of the dryer is always clean and be sure the dryer exhaust is unobstructed. Sometimes the termination cover can become clogged with lint or other objects. Also, use the exhaust vent located in the utility room when drying and washing clothes. Make sure that your HVAC filter fits properly within the grill opening. Many homes have “oversized” openings that standard filters cannot cover. If the filter opening is larger than the filter, use duct tape or some similar material to close the spaces – this ensures that “all” the particulates/dust are at least drawn across the filter membrane. As a builder, if you have concerns or need further information to eliminate dust problems; or to develop a ventilation strategy, please contact us @ 888-488-0206 – Guaranteed Watt Saver Systems, West.

Announcements...

Attention Builders –
GWSSI has received notification that GreenFiber is discontinuing their Engineered For Life Program effective November 1, 2004. They will continue to support all guarantees issued prior to this date but will no longer offer the program. If you are interested in other guarantee or advanced building science programs, please contact GWSSI for more information.

The Sunbelt Builders Show was a smashing successs!  To sum it up, here’s a message from Kathy Guidera - Executive Director of EEBA...
       Kelly,
             Please share this note with your staff - I cannot thank all of you enough for the hard work and effort you put into the show last week in Dallas! We have been talking for days about what a class act you all are and evidence of the time and effort you put into the events you were involved with - EEBA Applied looked great and got a lot of buzz. The BBQ at the ZEH was a success, too. Thanks again - you are all a pleasure to work with and EEBA thanks you!


The new ENERGY STAR logo has been officially introduced and the older logo should no longer be used after December 31,2004.  In order to make room in our inventory...
We are offering many of our products (listed below) at 50% off!
Take advantage of these prices while they last.  Quantities limited. Click here to order yours today.

Vinyl Decal
(3” x 3”) reg. price $0.90
Sale Price $0.45
(6” x 6”) reg. price $1.44
Sale Price $0.72

Static Cling Decal
(4” x 6”) reg. price $1.30
Sale Price $0.65

4-Color Literature Decals
(1,000 per roll) reg. price $102.00
Sale Price $51.00

Door Mats
(large) reg. price $186.00
Sale Price $93.00
(small) reg. price $110.00
Sale Price $55.00

Bronze Plaques
reg. price $12.50
Sale Price $6.25

Lapel Button
reg. price $1.05
Sale Price $0.50

Lapel Pin
reg. price $7.60
Sale Price $3.80

Mylar Balloons
reg. price $3.50
Sale Price $1.75

ENERGY STAR Video Clip
(CD) reg. price $5.00
Sale Price $2.50
(VHS) reg. price $20.00
Sale Price $10.00
(DVD) reg. price $40.00
Sale Price $20.00

ENERGY STAR Tip Cards
price depends on quantity ordered

Literature Stands
reg. price $7.50
Sale Price $3.75

If this E-mail does not display correctly, click here to view in your web browser

Plain Text Version