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Building & mechanical system energy conservation:
These articles describe how to substantially reduce building energy usage and costs: building heating and cooling costs, electric bills, and heating fuel bills.
We describe how to make use of solar energy or wind energy, and we detail other energy saving steps for homes and commercial buildings: building air leak detection / sealing, optimum building insulation, energy efficient ventilation, home heat loss detection / remedy, heating system tuneup / adjustments, setting priorities on energy saving steps (get the most return on your energy-savings dollar), and selecting energy efficient windows and doors. Page top: photo-voltaic system installed over a restaurant patio, Guanajuato.
US Financial crisis increases building owner focus on do it yourself home repair & saving heating & cooling costs and interest in Do-It-Yourself Building Repairs found here.
Links at the "More Reading" links at the bottom of this article identify major energy-conservation or energy savings topics that we discuss. A list of key energy cost reducing articles is provided just below. Sketch at page top is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss, and discussed
at ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE.Sketch at left shows a solar water heating system, courtesy of Lennox Industries.
AIR LEAK DETECTION TOOLS - how to find and fix air and heat leaks on buildings, an expert guide to weatherization. Air leaks in older homes overwhelm even high-R insulated walls and ceilings, increasing energy costs
FREEZE-PROOF A BUILDING - protect from frozen burst pipes, subsequent leaks, mold, water damage in colder buildings
Green Construction, Green Building Guidelines & Advice
International Green Construction Code (IGCC) Public Version 2.0, Novembrer 2010 (PDF file), retrieved 12/12/10, original source: http://www.iccsafe.org/CS/IGCC/Pages/IGCCDownloadV2.aspx?r=igccv2
International Green Construction Code (IGCC) - Water Efficiency Provisions Public Version 2.0, Novembrer 2010 (PDF file), retrieved 12/12/10, original source: http://www.iccsafe.org/CS/IGCC/Pages/IGCCDownloadV2.aspx?r=igccv2 LEED GREEN BUILDING CERTIFICATION LEED Building Designation & IAQ
HOUSE DOCTOR, how-to be - education, training, tools, publications for house doctors: air leaks, heat loss, building energy loss diagnosis and cure
HOUSEWRAP AIR & VAPOR BARRIERS - Guide to Selecting & Using Sheathing Wrap - House Wrap - Building Exterior Moisture Barriers - house wrap plays a critical role in stopping air leaks and heat losses, even on well-insulated buildings
The green power solar electrical panel array shown above is distributed by Desmex Solar and is installed in San Miguel de Allende, Mexico. This solar energy system provides all of the electrical energy required by a small restaurant, including powering lighting and nine refrigerators and coolers in the building.
SOLAR ENERGY SYSTEMS - passive solar, thermal mass, window glazing, building insulation and ventilation, sunspaces cut energy costs
PASSIVE SOLAR DESIGN KEY ELEMENTS - what are the key elements in passive solar design? - US DOE (supplemented with additional photos, commentary, text) - Online text
Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf
Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]
Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf
"Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.
In the United States, electricity is generated primarily from the combustion of a limited supply of fossil fuels, or with large hydroelectric dams, or with nuclear power plants. Each of these traditional approaches presents unique environmental concerns. Renewable energy dramatically lowers pollution emissions, reduces environmental health risks, and slows the depletion of finite natural resources.
Renewable energy is derived from sun, wind, water, or the Earth's core. It also can be derived from biomass—or plant matter—which is grown, harvested, and transferred into energy by one of a number of processes. Renewable technologies are designed to capture and store this energy. They include:
Transpired solar collectors use sunlight to preheat air for heating purposes. - see SOLAR ENERGY SYSTEMS
Solar hot water heaters use the sun to heat water for domestic applications. - see SOLAR ENERGY SYSTEMS
Small-scale hydroelectric power plants flow water over turbines, which turn a generator and create electricity.
Fuel cells combine hydrogen and oxygen to produce electricity and heat.
Ground-source heat pumps transfer heat to the ground in summer and extract heat from the ground in winter.
Green power is electricity generated from renewable sources such as wind, geothermal, biomass, and landfill gas.
Because use of renewable energy sources can involve purchase of equipment (solar collectors, wind generators) early in the development life of those systems, and because analysis of the economic costs can be complex, readers should review the topics listed above and at the "More Reading" links at the bottom of this article , and in particular, also see energy savings articles listed at
Home Mortgage Assistance for Buying Already-Energy-Efficient buildings
The Energy StarProgram defines a variety of home mortgage options that can give home owners or home buyers assistance for energy-efficient buildings. Readers should notice that these programs are aimed at purchasers of homes that are surveyed and rated as energy efficient before the purchase - not to finance energy improvement retrofits. However, there may be federal or local programs that do provide financial assistance for building weatherization and insulation retrofits.
Check with your local building department, state, town, or county financial assistance offices, and office for the elderly or aging in your community. Also check with building renovation programs intended to help people who own their home but are of very limited financial means, such as the Christmas in April program.
An Energy Efficient Mortgage (EEM) is a mortgage that credits a home’s energy efficiency in the mortgage itself. EEMs give borrowers the opportunity to finance cost-effective, energy-saving measures as part of a single mortgage and stretch debt-to-income qualifying ratios on loans thereby allowing borrowers to qualify for a larger loan amount and a better, more energy-efficient home.
To get an EEM a borrower typically has to have a home energy rater conduct a home energy rating before financing is approved. This rating verifies for the lender that the home is energy-efficient.
EEMs are typically used to purchase a new home that is already energy efficient such as an ENERGY STAR qualified home.
The term EEM is commonly used to refer to all types of energy mortgages including Energy Improvement Mortgages (EIMs), which are used to purchase existing homes that will have energy efficiency improvements made to them. EIMs allow borrowers to include the cost of energy-efficiency improvements to an existing home in the mortgage without increasing the down payment.
EIMs allow the borrower to use the money saved in utility bills to finance energy improvements. Both EEMs and EIMs typically require a home energy rating to provide the lender with the estimated monthly energy savings and the value of the energy efficiency measures — known as the Energy Savings Value.
EEMs (and EIMs) are sponsored by federally insured mortgage programs (FHA and VA) and the conventional secondary mortgage market (Fannie Mae and Freddie Mac). Lenders can offer conventional EEMs, FHA EEMs, or VA EEMs.
Conventional Energy Efficient Mortgages described by Energy Star
Conventional EEMs can be offered by lenders who sell their loans to Fannie Mae and Freddie Mac. Conventional EEMs increase the purchasing power of buying an energy efficient home by allowing the lender to increase the borrower’s income by a dollar amount equal to the estimated energy savings. The Fannie Mae loan also adjusts the value of the home to reflect the value of the energy efficiency measures. For more information about Fannie Mae's EEM you can call 1-800-7FANNIE (732-6643).
FHA Energy Efficient Mortgages described by Energy Star
FHA EEMs allow lenders to add 100 percent of the additional cost of cost-effective energy efficiency improvements to an already approved mortgage loan (as long as the additional costs do not exceed $4000 or 5 percent of the value of the home, up to a maximum of $8000, whichever is greater). No additional down payment is required, and the FHA loan limits won’t interfere with the process of obtaining the EEM. FHA EEMs are available for site-built as well as for manufactured homes. Applications for an FHA EEM may be submitted to the local HUD Field Office through an FHA-approved lending institution.
VA Energy Efficient Mortgages described by Energy Star
The Veteran’s Administration (VA) EEM is available to qualified military personnel, reservists and veterans for energy improvements when purchasing an existing home. The VA EEM caps energy improvements at $3,000–$6,000. Borrowers should ask their lender about a VA EEM at the beginning of the lending process.
To learn more about EEMs contact Fannie Mae, Freddie Mac, the FHA or the VA. Additional information about writing energy-efficient mortgages can be found on their Web sites.
ENERGY STAR Mortgages described by Energy Star at their Website
An ENERGY STAR mortgage pilot program is underway to demonstrate that financing can be a useful tool for enhancing the success of investing in energy-efficient homes by lowering borrowing costs, as well as demonstrating the importance of utilizing a network of qualified energy auditors and contractors to ensure that cost-effective energy efficiency improvements are realized.
By incorporating the costs of energy efficiency improvements into the loan itself, an ENERGY STAR mortgage allows borrowers to pay for those investments over the life of their loan and deduct the interest from their federal and state income taxes. One of the key benefits of an ENERGY STAR mortgage is that a borrower can finance and make energy-saving improvements to their homes without paying more for financing than they would for a typical mortgage. Participating lenders also offer borrowers an additional financial benefit above and beyond the value of the home energy savings, such as discounted mortgage rates, reduced loan fees, or assistance with closing costs.
Radiant floor heating vs cooling: what about a balance between summer cooling and winter heating
In south central Tennessee near Alabama we are building a small 1700 ft2 home. Three sides and the roof are completely enclosed in hillside soil with a 2 feet of soil over roof. We are installing radiant floor heating with an air handler back-up. Both will be hot water heated via wood burning boiler.
We have an annual temperature range from the low teens to the high nineties (degrees F). Our intention is to employ edge insulation but NOT floor insulation on the concrete slab floor. Our thinking is this will allow for radiant cooling in the summer and we will “pay” a manageable cost in performance during the winter.
We are pouring in two weeks and would greatly appreciate a response to this question: ARE WE ABOUT TO MAKE A BIG MISTAKE? Thanks. Sincerely Jim and Larry - Homeowners doing the work.
Reply: Match the building insulation plan and heating and cooling design to the climate
Steven Bliss & Daniel Friedman
Jim and Larry, your project is far enough south that the benefit from cooling, using the earth as a heat sink or a source of cooling in hot weather may outweigh the cost of heating in cool weather.
I have been very critical of uninsulated slabs in cold climates where the heating load is significant (see RADIANT HEAT FLOOR MISTAKES) . But I did not intend to suggest that in a climate where cooling costs are high that the data works out to the same conclusion nor that all buildings should have the same design regardless of climate.
Radiant Heating vs Radiant Cooling Floor Design Contrasts
Just to get a technical point out of the way, while we may speak of "radiant heating" it does not quite work the same way to speak of "radiant cooling". That is, a warm floor surface may heat surrounding objects by radiant heat - a method that many homeowners say is quite comfortable. But during hot weather a cooler floor doesn't "radiate" coolness - it won't blow cool air as does a conventional air conditioner or heat pump (though it might - see our article recommendations below).
Rather, heat radiating from hot or warm objects in the room will find some absorption by the cooler floor surface. So the room is radiating heat back to the floor, though I suspect with less efficiency in cooling mode than in heating mode. Why?
A large warm floor surface has an easy time radiating heat upwards into a cooler room area and onto objects in that room, as warmer air at the floor surface and around objects rises. Heat and warmth and warm air tend to move upwards in warm buildings - away from, rather than towards the floor.
I'm not sure it's as easy to move heat "down" in a passive design. In sum, while I think of radiant heating as an understandable approach to warming a building, I don't think of "radiant cooling" sending "coolness upwards" into the occupied space. Coolness won't move up, but heat may move down, a bit.
Compare Construction Costs vs. Energy Costs to Heat & Cool over Building Life
You'll want to estimate cooling and heating costs including anticipated energy cost rises in the future as well as energy cost comparisons between electric and fossil fuels, depending on how you are going to heat vs cool the home.
One could certainly compare two designs:
A: Summer cooling making use of the heat-absorbing properties of an uninsulated floor slab in good thermal contact with the cooler earth below, paying higher heating costs during the heating season due to heat losses through the floor.
B. Summer cooling making use of the heat-absorbing properties of an insulated floor slab and thermal mass below the slab, still insulating the slab from the earth below, making use of the same slab as a heat sink and reservoir during the heating season. This approach may save on energy costs but will have a higher build cost.
Thermal Mass and Building Energy Costs: reduced cooling loads in some climates
High-mass houses have been studied extensively by the log home industry and concrete industry through sophisticated computer modeling and field testing. They were intent on proving that the “mass effect” of high-mass buildings helped save energy independent of the R-value of the components. Their goal was to prove that log homes or, in the case of the concrete industry, concrete homes were inherently energy-efficient. Their efforts were somewhat successful in that ASHRAE, the organization that sets standards for the thermal performance of buildings now recognizes that thermal mass plays a modest role in a building’s performance (see ASHRAE Standard 90.1).
The benefit is mainly to reduce cooling loads in climates with hot days and cold nights. It does this by damping the temperature swing inside the space. Think adobe buildings in the high, arid Southwest where it may be 90°F during the day and 40°F at night. The high mass walls will keep the indoor temperature closer to the average of these two temperatures and thus more comfortable – reducing or eliminating the need for mechanical cooling, especially in arid areas where dehumidification is not needed.
When the outdoor temperatures are above the human comfort level, both day and night, such as in Florida in summer, thermal mass has much less value. It will cause a lag in the indoor peak temperature, relative to outdoors, but that may and may not be beneficial.
Thermal mass has less benefit for heating, and probably no benefit in cold climates when the winter temperature stays below the comfort level all day and night -- as in the northern U.S. in winter. One effect of a high-mass home, is that it is difficult to quickly heat up the house – which is why setback thermostats are not recommended in homes with radiant slabs. It’s also why direct-gain passive solar homes perform poorly in cold, cloudy weather. If the thermal mass is allowed to cool off during these periods, it takes a long time to heat up the building and the mass provides radiant cooling – when you need it the least!
Balanced Temperature Swings & Thermal Mass Benefits
One can observe that at locations where average day and night temperatures swing just about the same around a comfortable indoor temperature range, thermal mass alone can provide significant comfort in buildings and much less outside energy may be needed to heat or cool the home.
At PASSIVE SOLAR HEAT PERFORMANCE
at PASSIVE SOLAR HOME, LOW COST we illustrate homes located at an elevation of about 6300 ft. in central Mexico. Although it's not quite in perfect balance, a home in San Miguel de Allende (described at x) has been considered by its occupants (DF & family) to be comfortable enough as to not require central heating nor air conditioning. The structure, built of plastered adobe and concrete, has a high thermal mass. Passive solar gain warms the structure during the day, providing heat that is returned in cooler evenings; during warmer parts of the day the still-cool mass of the structure helps keep indoor temperatures comfortable.
At Technical Reviewers & REFERENCES we include references to other sources on this topic. Reference  seems to contain an error, in the section: “Nearly all areas with significant cooling loads can benefit from thermal mass in exterior walls. The sunny Southwest, particularly high-elevation areas of Arizona, New Mexico and Colorado, benefit the most from the mass effect for heating.” I think they meant to say “cooling.” Reference , a blog posting of the same information, gets this right.
Mass-Enhanced "R" Value
In a thoughtful article about mass-enhanded R-value, BuildCentral reports that while thermal mass can outperform low-mass building walls (or in your case floors) of the same R-value, deciding if a particular building will benefit from this design requires some careful thought. Quoting:
The mass effect is real. High-mass walls really can significantly outperform low-mass walls of comparable steady-state R-value--i.e., they can achieve a higher "mass-enhanced R-value." BUT (and this is an important "but"), this mass-enhanced R-value is only significant when the outdoor temperatures cycle above and below indoor temperatures within a 24-hour period. Thus, high-mass walls are most beneficial in moderate climates that have high diurnal (daily) temperature swings around the desired indoor setpoint. 
Thermal Mass & Passive Solar Energy Systems for Heating, Cooling, or Both
And at FLOOR CHOICES OVER CONCRETE SLABS we illustrate a floor slab (with incomplete under-slab insulation) that provides thermal mass helping to stabilize temperatures in a cabin in torthern Minnesota.
We no longer recommend solar rock bins as thermal mass or for thermal storage. These were largely discredited by Solar Age and others as ineffective, expensive, and prone to all manner of problems with mold, poor airflow, etc.
As for modeling thermal mass effects and earth-sheltering, it’s usually done on mainframes using DOE BLAST, so it’s not for the faint hearted or anyone else who doesn’t have a PhD in physics.
Thermal Mass & Active Solar Energy Systems for both Heating & Cooling
Both of those approaches presume that the thermal mass is nevertheless insulated from the earth, so that it can benefit both heating and cooling seasons.
In sum, my OPINION is that you are considering a design that has appeal for simplicity and lower installation cost. But before deciding you might want to look at both active and passive solar designs that make use of thermal mass, often an insulated thermal mass, to reduce both summer cooling and winter heating costs.
Steven Bliss adds:
I did a follow-up where-are-they-now study once at Solar Age, looking at well-known solar and alternative houses including a couple of earth-sheltered houses built by Malcolm Wells, one of the widely published proponents of living underground. To make a long story short, I contacted the owners who had recently removed all the earth from their roof due to mysterious pinhole leaks in the rubber roof, which maybe wasn’t designed to have tons on earth overhead.
Living underground is not for everyone – anymore than everyone would want to live in someone’s basemet
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