Need advice on building an energy efficient house

bnicebkindJune 4, 2004

Our home construction has started about 1 month ago in Florida. It is in a subdivision, on the water. We have designed the home with large overhangs ( i.e.wrap around porches) and huricane glass insulated low e solar windows. The house is designed to have a metal roofing system. Would this be efficient? What are your recommendations on other ways to make it efficient? What air conditioning (and heat) system do you recommend? All ideas and advice are welcome!

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There is an excellent website called floridasolarsite dot com. In florida one can easily generate all one's pv power and heat water year-round with a solar batch heater.

Be sure the metal roof is white or aluminized in color for maximum heat reflection. Typical suburban architecture with large dark-colored roof surfaces are very bad for energy efficiency in the south.

    Bookmark   June 6, 2004 at 7:25AM
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How far along are you in the construction process? What kind of house are you building? The advice people can give you will depend on that.

    Bookmark   June 6, 2004 at 9:03AM
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They just finished the foundation and the first floor exterior cement block. We are building a home with deep overhangs (wrap around porches) in the front and the back of the house. the house will have hardiplank exterior. 2 story house. I understand that they are making strides in the roofing/solar industry, where they are weaving the solar into the roof shingles! pnbrown: what is a solar batch heater??? all info to educate me is very welcome!

    Bookmark   June 7, 2004 at 4:45PM
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Unfortunatly, now that you've started to build a number of energy saving options aren't possible, for example passive solar. The best energy saving houses are designed to save energy from the very first plan, but you still have plenty of options left to make it more energy efficient.

The best thing you can do is insulate properly. At the very least, use the minimum R value recomended in your area for the walls and roof. Personally, however, I would use more as insulation is cheap, reliable and works for the life of the building. Also, installing a larger ammount of insulation may allow you to purchase smaller HVAC equipment which makes it even more affordable. The type of insulation is also important. There's nothing terribly wrong with the normal pink rolls, they just aren't the best product. They tend to settle in the walls and leak air. Spray insulation plugs most the air infiltration and never settles. I like rockwool as it never rots, cannot burn, doesn't feed insects/rodents and doesn't contain any toxic chemicals.

Another angle to look in to is radiant insulation. Normal insulation slows convected heat by creating lots of air gaps, but it does almost nothing to slow radiant heat which is a major energy loss in most houses. It's quite thin and can be added on top of regular insulation to gain the benifits of both without thickening the walls.

Also, the higher the HVAC effciency the better. The difference between a normal 80% furnace and a 93% furnace is of course a consistent lowering of your heating bills by 13%. If you're intending to live in a house for more than a few years, higher efficiency will pay for itself. It also adds a little to the house value.

Finally, if you're installing ductwork it's important to seal it properly. Duct tape has been proven by many tests to be rubish for sealing ducts. I've read several studies that claimed most houses, both old and new, leaked a third of their heated/cooled air through ductwork leaks in to the walls and roof. Mastic or heavy duty caulk is ideal for sealing ductwork, and it's best to do the job properly now as you cannot easily go back and fix it once the walls are plastered.

    Bookmark   June 7, 2004 at 6:41PM
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White or reflective metal roofing is the best as
it reduces heat gain into attic. Radiant barriers
are also recommended for our climates.
Visit Florida Solar Enegy Center for more radiant
barrier info. and more information.

Here is a copy of the spec sheet that I give my
clients. If you have more specific questions,
please let me know and we will address them.
These are the requirements for an Energy Star home.
I hope that this will answer some of your questions.

Summary of Energy Efficiency Specifications

Air Infiltration Goal is .35 Natural Air Changes per Hourheating. Gaskets such as Owens-Corning FoamSeal R or Dow Sill Seal between sole plate and slab is recommended. For 2nd story or bonus rooms, insulate and seal openings between floor joists, under walls with foam board sheathing material. Seal all windows and doors jambs with minimal or non expanding foam.
Seal all wire penetrations especially those through top plate. Incorporate Airtight Drywall Approach throughout home. Run sheetrock all the way to bottom plate behind showers and tubs, seal plumbing penetrations under tubs especially on upper floors. Minimize use of recessed lights or install Insulation Contact Air Tight (ICAT) lights. Existing recessed lights that are not air tight can be retrofitted with air tight trim kits. Get name brand and model numbers of lights to order trim kits.

Windows Double-glazed with Low-E glass and non-heat-conducting frames are recommended. Look for U-vales and SHGC (solar heat gain coefficient) of less than .4 for best performance in this area. Go to to learn more about window types and labels on windows.
DOORS Steel, polyurethane foam core (R 2.5 to 5.0) with high quality weather-strip. Solid wood door with double-glazing allowed for front door. Exterior-type foam-core doors with good air seals on doors to all attic spaces and kneewalls.
Walls 2x4 walls R-15 un-faced insulation with double sided 1" foil sheathing boards. 2x6 walls R-19 also with double sided foil sheathing boards.
Face unprinted side to exterior. Sheathing must cover top plate to sole plate. Seal all seams with foil tape. Use ½" foil sheathing in between 2X headers instead of plywood. Insulate behind tub and shower units before installing units.

Ceilings R-30 minimum with a Radiant Barriers are recommended for this climate. Visit Florida Solar Energy CenterÂs web site for more information on radiant barriers
Seal and insulate attic accesses when in the conditioned areas. If attic staircase s in conditioned area, seal with attic tent or build a box with 2x12 with ½" plywood for top, insulate and weather-strip to seal well.
Use Energy efficient (O.V.E.) framing at corners and partition walls, See LaDNR BuilderÂs Guide To Energy Efficient Homes in Louisiana or Doug Rye video.
Continuous ridge vents ( with wind baffles) and continuous soffits vents. One square foot of net free area for every 150-sq.ft. of attic floor space, divided equally between ridge and soffits vents.


Duct Leakage and Insulation Duct loss must be no more than 5%. Before insulating hard pipe seal all joints & seams. Use Mastic or an approved UL-181 rated mastic tape, such as Hardcast tape.
Have HVAC contractor size A/C system using Manual J. Design duct layout using Manual D. Upgrade insulation values from a standard R-4.2 to R-6 or R-8 is recommended.
Water Heaters Compare Energy Factors (E.F.) Gas E.F. of .65 on a standard tank and E.F. of .95 on an electric standard tank. Adding an insulating blanket can also increase the efficiency of water heaters. Instant, tankless gas water heaters have higher E.F. of .85. The most efficient for electric Heat Pump water heaters (also called heat recovery or desuperheaters) provide 90% to 100% free hot water in summer months.

Cooling 12-14 SEER, 0.75or less Sensible heat fraction (SHF) mandatory minimum requirement.
Two speed or variable speed system if over-sizing of tonnage . Consider
Zoned system versus multiple units. 700 sq. ft. per ton as opposed to old
rule-of-thumb of 400 to 500 sq. ft. per ton. Bigger is not better!

Heating Gas furnace AFUE 80% minimum. Efficiency on these units up to 94% (condensing unit with PVC flue). For Heat Pumps specify a minimum of HSPF of 8.0. Variable speed heat pumps will have up to 9.0 HSPF.

Lighting Use fluorescent lighting whenever possible. Compact Fluorescent in all fixtures like recessed lights. IC Air Tight recessed lights are mandatory requirements. Existing recessed lights can be retrofitted with air tight trim kits available at lighting stores and box outlets.
Appliances Purchase Energy Star Appliances for high efficiency, especially refrigerators, freezers and water heaters which run 24/7. Look for Energy Guide labels in the lower range for more efficiency.

    Bookmark   June 12, 2004 at 1:05PM
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Energy Rater- why no attic power vents?

    Bookmark   June 14, 2004 at 6:25PM
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Why use electricity to do something
that occurs naturally?
That is always my first thought, but what
diagnostics have taught me is that
power vents pull conditioned air out
of the house through unsealed areas
into the attic. There are many areas of
air infiltration from the attic, folding staircases,
plumbing walls and penetrations, unsealed bath
vent fans and stove vent fans, to list a few.

The theory behind power vent fans is that they
take air in from the soffits. Good theory, but not
always realistic. What they actually do is pull air from
wherever they can get it. If venting is restricted
as in a lot of older homes, they pull even more
from the conditioned space.

I recently went to a home where they installed
4 power vents in the attic. The heating system was
located in a closet in the conditioned area. The door
to the system was uninsulated and not weather stripped,
plus open at top to attic.
The homeowner complained about how much hotter his
house was, and the a/c guys said it was cool when they
were workig in the attic. 500 cfm of conditioned air
into attic was what my testing showed.
Unplugged the power vents, sealed heating closet
porblem solved. (well not that easy! there were
leaky recessed lights, unsealed shower units...)
The latter is in the works, but the closet we
sealed then and retested. An hour later the
house was cooling better than it ever had.

The power vent is a discussion that can get pretty
heated. Similar to the tyvek/felt and
ventilated/unventilated attic debates.

    Bookmark   June 15, 2004 at 9:21AM
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Perhaps you would be interested in the article I wrote regarding energy conservation. Air leaks are the largest source of heating and cooling loss, resulting in increased energy costs. The same air leaks that cost us heat loss in the North can cost you cooling loss in the South.

Mark D. Tyrol, P.E.
Battic Door Attic Stair Covers
PO Box 15
Mansfield, MA 02048-0015
tel. 508.320.9082
fax 508.339.4571

Reduce Your Heating Bills This Winter - Overlooked Sources of Heat Loss in the Home, by Mark D. Tyrol, P.E., - November 2004

Imagine leaving a window open all winter long the heat loss, cold drafts, and wasted energy! Well if your home has a folding attic stair, a fireplace, and/or a clothes dryer, that may be just what is occurring in your home!

These often overlooked sources of heat loss and air leakage can cause your heat pour out and the cold outside air pour in costing you higher heating bills, causing cold drafts, and wasting energy.

Air leaks are the largest source of heating and cooling loss in the home. Air leaks occur through the small cracks around doors, windows, pipes, etc. Homeowners are well aware of the benefits of applying caulk and weatherstripping to these areas to minimize heat loss and cold drafts.

But what can you do about the three largest "holes" in your home the folding attic stair, the fireplace, and the clothes dryer? Here are some tips and techniques that can easily, quickly and inexpensively seal and insulate these holes.

Attic Stairs:

Do you have a folding attic stairway in your house? When attic stairs are installed, a large hole (approximately 10 square feet!) is created in your ceiling. The ceiling and insulation that were there have to be removed. And what is installed to cover this opening? A thin, unsealed, un-insulated sheet of plywood!

Did you know that your attic space is ventilated directly to the outdoors? In the winter, the attic space can be very cold, and in the summer it can be very hot. And what is separating your conditioned house from your unconditioned attic? That thin sheet of plywood!

Often a gap can be observed around the perimeter of the door. Try this yourself: at night when it is dark, turn on the attic light and shut the attic stairway door - do you see any light coming through? These are gaps - which add up to a large opening where your heated/cooled air leaks out 24 hours a day, 7 days a week, 52 weeks a year! This is like leaving a window open all year round!

An easy, low-cost solution to this problem is to add an attic stair cover. An attic stair cover provides an air seal, reducing the air leaks. Add the desired amount of insulation over the cover to restore the insulation removed from the ceiling.


Approximately 100 million homes in North America are constructed with wood or gas burning fireplaces. Unfortunately there are negative side effects that the fireplace brings to a home especially during the winter home-heating season. Fireplaces are energy losers!

Researchers have studied this to determine the amount of heat loss through a fireplace, and the results are amazing! One remarkable research study showed that an open damper on an unused fireplace in a well-insulated house can raise overall heating energy consumption by 30%!

A recent study showed that for many consumers, their heating bills may be more than $500 higher per winter just due to the air leakage and wasted energy caused by fireplaces!

Why Does a Home With a Fireplace Have Higher Heating Bills? Hot air rises! Your heated air leaks out any exit it can find, and when your warm heated air is drawn out of your home, cold outside air is drawn in to make up for it. The fireplace is like a giant straw - sucking the heated air from your house. This is like leaving a window open all year round!

An easy, low-cost solution to this problem is to add a fireplace draftstopper. A fireplace draftstopper is an inflatable pillow that seals the damper, eliminating any air leaks. The pillow removed whenever the fireplace is used, then reinserted after.

Clothes Dryer Exhaust Ducts:

Have you ever noticed that the room containing your clothes dryer is the coldest room in your house? Ever wonder why? Your clothes dryer is connected to an exhaust duct that is open to the outdoors. In the winter, cold air leaks in through the duct, through your dryer and into your house, while your heated air just pours right out!

Dryer vents use a sheet metal flapper to try to reduce this air leakage. This is very primitive technology that does not provide a positive seal to stop the air leakage. Compounding the problem is that over time, lint clogs the flapper valve causing it to stay open. This is like leaving a window open all year round!

An easy, low-cost solution to this problem is to add a dryer vent seal! A dryer vent seal will reduce unwanted air infiltration, and keep out pests, bees and rodents as well. The vent will remain closed unless the dryer is in use. When the dryer is in use, a floating shuttle rises to allow warm air, lint, and moisture to escape.

If your home has a folding attic stair, a fireplace, and/or a clothes dryer, you can easily, quickly and inexpensively seal and insulate these holes. At Battic Door, we have developed low-cost, green solutions to these and other energy-conservation related issues. For more information please visit our website or send a S.A.S.E. to P.O. Box 15, Mansfield, MA 02048.

    Bookmark   November 13, 2004 at 10:27PM
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