Solar electrical power array, San Miguel de Allende (C) Daniel FriedmanBuilding Energy Savings Methods

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Building & mechanical system energy conservation:

Guide to articles describing how to substantially reduce building energy usage and costs: building heating and cooling costs, electric bills, and heating fuel bills. Energy Efficiency Designs, Inspections, Tests, & Retrofit Improvements for buildings. How to Cut building heating, cooling & other operating costs.

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 tune up / 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.

Also try the page top or bottom SEARCH BOX as a quick way to find information you need.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Energy Conservation Guides for Buildings

Schematic of a solar water heater hookup (C) - Lennox IndustriesIn addition to the index to key building energy loss, analysis, troubleshooting & savings articles given here, at the MORE READING links at the bottom of this article you can find our master index to energy-conservation or energy savings topics found at this website.

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 above/left shows a solar water heating system, courtesy of Lennox Industries. [Click to enlarge any image]

To find what you need quickly, if you don't want to scroll through this index you are welcome to use the page top or bottom SEARCH BOX to search InspectApedia for specific articles and information.

Air and heat loss sealing points in buildings (C) Daniel Friedman

Solar electrical power array, San Miguel de Allende (C) Daniel Friedman Solar electrical power array, San Miguel de Allende (C) Daniel Friedman

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.

Qualified service providers specializing in topics discussed at this website may (at our discretion) be listed at this website at no fee.

U.S. EPA Description of Types of Renewable Energy Sources

Onsite Renewable Technologies - US EPA List:

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:

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 Star Program 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.

According to EnergyStar, (quoting from the Energy Star source - at reviewers section of this page)

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

Reader Question:

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.


and 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 has been considered by its occupants (editor & 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 [2] 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 [3], a blog posting of the same information, gets this right.

Mass-Enhanced "R" Value

In a thoughtful article about mass-enhanced R-value, Build Central 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. [4]

Thermal Mass & Passive Solar Energy Systems for Heating, Cooling, or Both

We discuss thermal mass in building floors in passive solar designs




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 northern 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

Take a look at

Active Solar Rock-bed Heat Storage Design Details: Active Solar Energy Systems, and also Active Solar Blockbed Floor Design for examples of using thermal mass to control both heating and cooling cost, and in the case of the second article, including active cooling by routing building air through passages in the thermal-mass of a cool floor.

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 basement


Continue reading at AFUE DEFINITION, RATINGS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Suggested citation for this web page

ENERGY SAVINGS in BUILDINGS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman