Books for Homeowners Interested in Saving Energy

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Books for Homeowners Interested in Saving Energy

These two books are among the best books out there — but they are still disappointing

Posted on May 8 2015 by Martin Holladay

Two books that do a good job of explaining residential energy use issues to homeowners are Consumer Guide To Home Energy Savings and No-Regrets Remodeling. Both books have been around for years. Recently the publishers of these two books issued new editions, so I decided to give them a careful read.

Consumer Guide To Home Energy Savings

Since 1990, the American Council for an Energy-Efficient Economy (ACEEE) has published the Consumer Guide To Home Energy Savings. The current version is the tenth edition; its authors — Jennifer Thorne Amann, Alex Wilson, and Katie Ackerly — are the same as those of the ninth edition.

This book is an excellent homeowner’s guide to reducing home energy use. The authors make a stab at addressing basic building science concepts — for example, by explaining what a thermal envelope is, and by discussing the importance of air barriers. Most of the book’s information is accurate and helpful.

Yet the book is occasionally troubling and ultimately unsatisfying — both for its many errors and its fundamental failure to help homeowners focus on what matters most. The authors seem to lurch from topic to topic, in an apparent attempt to be comprehensive, without providing enough context to help homeowners distinguish between trivial and crucial issues.

Examples of misplaced emphasis abound:

  • The book includes 8 pages on buying new windows (an energy-saving measure which is almost never cost-effective) but only 2 1/2 pages on fixing up existing windows.
  • The book includes 9 pages of tips on reducing energy used for cooking — tips which, even if followed conscientiously, will yield only trivial energy savings — but only 4 pages on sealing air leaks in building envelopes and only 2 pages on swimming pool pumps.
  • The book includes 21 pages on buying a new heating appliance, but only half a page on duct sealing.
  • The book includes 18 pages on selecting a replacement water heater, but only a small, easy-to-miss paragraph on drainwater heat recovery devices.

Is adding insulation to your attic a simple job?

The authors advise, “Adding insulation to an unheated attic is usually a lot easier [than adding insulation to walls]. If there is no floor in the attic, simply add more insulation.” The adverb “simply” is irksome.

Unfortunately, this section of the book forgot an important sentence: “Before adding more attic insulation, make sure that you have sealed all of the air leaks in the ceiling below.” While the book mentions air sealing elsewhere, readers need to be reminded that this type of work must follow a strict order: A before B.

How much insulation does an attic need?

The authors advise, “In most of the country, a full foot of fiberglass or cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection. is cost-effective in the attic floor.” But that’s only about R-40 or R-43 — less than minimum code requirements (R-49) for the northern two-thirds of the country.

Readers in “warm climates” are advised to install ceiling insulation that is between R-22 and R-38. But R-22 insulation is too thin to meet minimum code requirements anywhere in the country.

The best-selling type of window in America is…

The authors report that “wood is still the most common material in use” for window frames and window sash. Yet that hasn’t been true for many, many years. In 2012, vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). windows represented 68% of the residential window market while wood windows represented only 20%.

The book mentions a type of vinyl window I’ve never heard of: a window with “vinyl frames insulated with fiberglass.” Does this type of window even exist?

Vegetated roofs

The book claims that “green roof systems” (vegetated roofs) are “good for energy efficiency.”

Actually, a green roof provides a very low R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. per dollar invested. For a thorough discussion of this topic, see Seeing Red Over Green Roofs.

What should you do if your indoor air is dry during the winter?

The authors advise, “If you live in a dry climate (or a place with cold, dry winters), and it is uncomfortably dry inside, check the fan speed on any ventilation equipment you might have installed before running out to buy a humidifier.” Check the fan speed? What does that mean?

Presumably, the authors meant something like this: “If you have a whole-house mechanical ventilation system, and if the fan speed on your ventilation system is adjustable, you can try turning the fan speed down.” However, that’s not what they wrote.

Moreover, to reduce the ventilation rate on many types of ventilation systems (including central-fan-integrated supply ventilation systems), you don’t adjust the fan speed. The ventilation rate is reduced by adjusting a damper or by altering the settings on an electronic control module.

All that said, even a revised and clarified version of the confusing sentence amounts to bad advice. The authors should have written, “If your indoor air is too dry during the winter, that’s a sign that your home is very leaky (or, in some cases, overventilated). In most cases, the best solution is to plug the air leaks in your basement and attic.”

One more point: the fact that leaky houses tend to have dry indoor air during the winter has nothing to do with whether the house is located in a “dry climate.” This phenomenon is related to temperature, not precipitation. Even if you live somewhere that gets 6 inches of snow a day, this problem occurs.

Do you need to consult an engineer to install an HRV?

Are you considering installing an HRV? Here is the authors’ advice: “Balanced ventilation is essentially a well-controlled combination of the exhaust and supply [ventilation] strategies discussed above, but it takes a very tight house and good engineering.”

Of course, a very tight house is always a good idea — but if you want an HRV, you can certainly install one even if your house isn’t “very tight.” Moreover, most HRVs are installed without the help of an engineer.

The authors go on to write, “The relatively large electric power use of ERVs and HRVs generally make them a luxury option in mild climates.” This is entirely false.

Of the three main types of ventilation systems — exhaust-only, supply-only, and balanced systems (HRVs and ERVs) — HRVs and ERVs have the lowest operating costs. The reason that they don’t make sense in mild climates has nothing to do with their operating costs; it has to do with the equipment’s high purchase and installation cost.

What’s the COP of a ground-source heat pump?

The authors write, “Ground-source heat pumps, however, are much more efficient” than air-source heat pumps.

A more accurate sentence might be, “A perfectly designed and perfectly installed ground-source heat pump is usually more efficient than an air-source heat pump. As typically installed, however, these systems often perform at about the same efficiency as an air-source heat pump.”

Do furnace tune-ups save energy?

“Regular tune-ups [of furnaces and boilers] should cut heating costs. … A complete tune-up may cost more than $100, but can reduce your heating bill from 3% to 10%.”

Long propagated by HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. service techs, this myth has been soundly refuted by researcher after researcher. Michael Blasnik, an energy consultant in Boston, Massachusetts, explains, “There are no studies that demonstrate significant energy savings from tuning up gas furnaces, but there are studies that show no energy savings, and some that show no measurable improvements in steady-state efficiency after a tune-up. These studies are for older systems. For newer equipment, the potential value of a tune-up is even more remote. Annual tune-ups are just a waste of money and energy (since the contractor has to drives to your home).”

What type of duct tape should you buy?

The authors advise, “Unfortunately, non-UL181B duct tape will dry up and lose its adhesion over time.” The clear implication is that UL181B duct tape will not dry up and will remain tenacious over time.

Here’s what I wrote on the topic back in 2010: “According to tests performed at Lawrence Berkeley National Laboratory by Max Sherman and Iain Walker, a UL181 listing is no guarantee that a tape will last any longer than unlisted cloth duct tape. ‘In California, the duct-tape industry wanted the code to approve the use of UL181-listed products,’ says Walker. ‘But in our lab tests we have found that the UL181 products fail. Just because it is UL181 listed does not mean that it performs any better than non-UL181 listed products. The listed tapes may be of a higher quality — the mechanical properties of the tape are better — but they are not any better in terms of longevity at high temperature. Under those conditions the UL181 tapes failed as well as the non-UL181 tapes.’ ”

Should you close the dampers of HVAC ducts leading to unused rooms?

The authors advise, “Dampers and registers [in forced air systems] … can be turned down or off to control heat flow to various rooms. Unused rooms should be kept cooler than occupied rooms to save energy.”

Here’s what I wrote on the topic back in 2011: “To debunk this myth, [Michael] Blasnik quotes a study performed by Iain Walker, a staff scientist at LBNL: ‘The results of this study showed that register closing led to increased energy use for a typical California house over a wide combination of climate, duct leakage, and number of closed registers. The reduction in building thermal loads due to conditioning only part of the house was offset by increased duct system losses, mostly due to increased duct leakage.’ ”

Should you turn on your ceiling fan during the winter?

The authors advise, “In the winter, a clockwise motion [of your ceiling fan] creates an updraft that keeps warm air in the occupied space.”

Why won’t this myth die? I addressed the issue in a 2010 article: “The ‘destratification savings’ myth was debunked 17 years ago, when an article in the June 1993 issue of Consumer Reports pointed out that there is no evidence to back the claim that destratification saves energy. [Energy expert Arnie] Katz agrees. ‘In theory, ceiling fans can also save energy in the winter,’ Katz wrote. ‘To date, I’ve seen no research that demonstrates this actually happens in the real world.’ Needless to say, the use of ceiling fans (whether blowing air upward or downward) during the winter can actually make occupants less comfortable — since blowing air has a cooling effect.”

Does your air conditioner need to be shaded?

“The outside part of a central air conditioner — the condensing unit — should be located in a cool, shaded place.”

Actually, locating the condensing unit of an air condition in the shade instead of the sun won’t save any energy. See this Q&A thread for a discussion of this myth.

Is a solar water heater a good investment?

The authors write, “Solar water heaters can be a great investment because they offer a virtually cost-free and renewable energy source for one of your home’s top energy users.”

There are a couple of things wrong with this sentence. First of all, solar water heaters are not cost-free; they cost about $8,000 or $9,000. Second, even if the annual operating cost of a solar water heater were zero — it isn’t — the cost of the equipment is a fundamental part of the basic calculation to determine whether a piece equipment is a “great investment.”

Remarkably, Consumer Guide To Home Energy Savings includes a table that refutes the book’s claim that a solar water heater is a great investment. The table shows that a solar water heater paired with a gas water heater for backup saves $80 a year (compared to house that has only a gas water heater). If the solar water heater costs $5,000 — the cost estimate provided in the table — the simple payback period would be 82 years. That’s hardly a “great investment.” If the solar water heater costs $9,000 — a more realistic figure — the simple payback period would be 112 years.

Pack your freezer with plastic water bottles

The authors advise, “A full freezer will perform better than a nearly empty freezer. If your freezer isn’t full, fill plastic containers with water and freeze them.”

As I explained in a 2013 article, this energy-saving tip will never save enough energy to show up on your electric bill.

Tips to save energy when cooking

“You can probably save a lot of energy just by modifying your cooking habits,” the authors enthuse. They advise, “Copper-bottom pans heat up faster than regular pans.”

How many pennies per year does this tip save? Too few to count.

No-Regrets Remodeling

The second book under review, No-Regrets Remodeling, is published by the editors of Home Energy magazine. The new edition is a revised second edition of the book. First published in 2003, No-Regrets Remodeling is based on a series of articles that began appearing in Home Energy in 1995.

The book is written for homeowners who are planning a remodeling project. The book’s authors hope to nudge homeowners toward decisions that help lower their energy bills.

Having apparently decided that homeowners aren’t quite ready for in-depth technical discussions or how-to advice, the editors of the second edition of the book have eliminated several sections that appeared in the first edition. For example, the first edition of the book had a long chapter on air-sealing, providing step-by-step instructions for locating and sealing different types of air leaks. In the second edition of the book, most of the how-to details are gone. Rather than explaining (for example) all of the steps required to air-seal an attic, the authors advise homeowners to hire a home performance contractor.

Whether these edits weaken or strengthen the book depends on one’s perspective.

There is lots of good advice

Most of the technical information in the second edition of No-Regrets Remodeling is sound. Here is a sampling of the book’s excellent advice:

  • “Coupling PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. panels with a heat pump water heaterAn appliance that uses an air-source heat pump to heat domestic hot water. Most heat-pump water heaters include an insulated tank equipped with an electric resistance element to provide backup heat whenever hot water demand exceeds the capacity of the heat pump. Since heat-pump water heaters extract heat from the air, they lower the temperature and humidity of the room in which they are installed. or even an electric-resistance water heater is often more cost-effective than using a solar water heater.”
  • “People need to breathe, not houses.”
  • “Recessed can lights … should never be used in vaulted ceilings that are part of the building envelope.”
  • “For the kitchen exhaust hood fan, …avoid getting a fan that’s too powerful; it can cause negative pressures and backdraftingIndoor air quality problem in which potentially dangerous combustion gases escape into the house instead of going up the chimney..”
  • “Exhaust[-only] ventilation was once recommended only for homes in cold climates, but in tightly built homes with low airflow, it can be used in any climate.”

And yet…

Reducing energy used by refrigerators

In this book, the plastic water jug tip rears its ugly head again. Like the authors of Consumer Guide To Home Energy Savings, the authors of No-Regrets Remodeling advise readers, “If the refrigerator is only partly full, fill the rest of it with jugs of water to reduce energy use.”

Backyard wind turbines?

Admittedly, this statement in No-Regrets Remodeling is true: “Small-scale wind power may be an option if you have sufficient space and plenty of wind.”

Yes, it may be an option. The only problem is that it is a bad option, not a good option. Even homeowners with lots of land and plenty of wind are almost always better off with a PV system.

Defining U-factor and U-value

Is there any difference between U-factor and U-value? Not really — except for the fact that “U-factor” is the preferred term (because it is a mathematical factor in heat flow equations).

Inexplicably, the authors of No-Regrets Remodeling have invented a distinction where none exists. First, the authors correctly define U-factor as a synonym for “thermal transmittance,” explaining, “A material with an R-value of 10 has a thermal transmittance of 1/10, or 0.1.” Then they muddy the waters by introducing an utterly original (and false) definition for “U-value,” claiming that that U-value “represents the thermal transmittance at the center of the glass.” No, it doesn’t.

U-value — a synonym for U-factor — is the thermal transmittance of whatever assembly or material you are discussing.

What should you do if you have ducts in an unconditioned attic?

The authors advise, “Ducts outside conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. should be well sealed and insulated with rigid fiberboard, flexible fiberglass, flexible foam, and reflective insulation.”

The first problem with the sentence is the final “and.” The authors probably meant “or.” (If they meant “and,” that’s a difficult prescription to follow.)

The biggest problem with the sentence is that readers deserve a deeper discussion of the problem of ducts in unconditioned attics. This isn’t just a minor point — it’s one of the biggest problems in many existing homes. If a homeowner pokes her head into her attic and sees duct tape on the seams of the insulated flex duct, should she conclude, “OK — I’m all set”?

Powered attic ventilators

The authors advise, “In some situations, you may need a powered attic fan to rid the attic of excessive heat or moisture.”

Really? I invite the authors to describe one such situation. For an in-depth discussion of this issue, see Fans in the Attic: Do They Help or Do They Hurt?

Remodeling basements

The authors inform readers that “Basements can be ideal for remodeling into usable space.”

Assuming that the remodeler can find a way to deal with bulk water entry, inward moisture diffusion, air leakage, heat flow through concrete, the relocation of HVAC equipment, low ceiling problems, uninsulated slabs, stair riser height adjustments, and code-required emergency egress issues — yes, basements are ideal for this purpose. They are also good for storing coal.

Why is spray foam preferred for basement walls?

The authors write, “Although SPF [spray polyurethane foam] is expensive, it has several advantages over rigid foam [for insulating basement walls]: it controls moisture better, saves more energy, and makes a basement more comfortable — and it may allow you to downsize the mechanical system.”

This sentence contains several misstatements. First of all, there are two types of spray polyurethane foam: open-cell foam (a vapor-permeable insulation rated at about R-3.7 per inch) and closed-cell foam (a vapor-impermeable insulation rated at about R-6 or R-6.5 per inch). Open-cell spray foam does a worse job of “controlling moisture” — presumably, the authors are referring to limiting vapor diffusionMovement of water vapor through a material; water vapor can diffuse through even solid materials if the permeability is high enough. — than XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation. or foil-faced polyisoPolyisocyanurate foam is usually sold with aluminum foil facings. With an R-value of 6 to 6.5 per inch, it is the best insulator and most expensive of the three types of rigid foam. Foil-faced polyisocyanurate is almost impermeable to water vapor; a 1-in.-thick foil-faced board has a permeance of 0.05 perm. While polyisocyanurate was formerly manufactured using HCFCs as blowing agents, U.S. manufacturers have now switched to pentane. Pentane does not damage the earth’s ozone layer, although it may contribute to smog. , while closed-cell spray foam is no better at this task than XPS or foil-faced polyiso.

Polyiso has the same R-value per inch as closed-cell spray foam, and a higher R-value per inch than open-cell spray foam, so it’s a mystery why the authors think that spray foam “saves more energy.”

Finally, I’m at a loss to come up with any scenario that explains the mysterious statement that spray polyurethane foam will “make a basement more comfortable” than rigid foam insulation.

Homes with HRVs still need a bath exhaust fan?

The authors declare categorically, “If you install an HRV or ERV, you will still need a separate range hood in the kitchen and an exhaust fan in the bathroom.”

Actually, the situation is more complicated than the categorical statement in this sentence. For a thorough discussion of the topic, see Does a Home with an HRV Also Need Bath Fans?

Are combustion appliances toxic?

The authors state, “Combustion appliances — fueled by propane, natural gas, kerosene, oil, or wood — are another source of indoor pollutants. They produce toxic gases and tiny particles that pollute indoor air.”

In fact, most combustion appliances — including furnaces and water heaters — will not pollute indoor air with “toxic gases” unless there is a fundamental design or installation flaw.

Supply ventilation systems in cold climates

The authors advise, “Adding a central supply system [that is, a central-fan-integrated supply ventilation system] is not recommended in cold climates, where you don’t want to force warm, moist air into cold walls or ceilings. This can quickly lead to condensation, mold, and rot.”

In fact, this type of ventilation system is routinely installed in cold climates. If properly designed and installed, these systems should ventilate at a rate of 50 cfm to 100 cfm in most homes — an airflow rate that is too low to cause the “condensation, mold, and rot” problems envisioned by the authors of No-Regrets Remodeling.

When you remodel your house, should you add thermal mass?

“Remodeling gives you a chance to expose masonry or stone already build into your house to direct sunlight, and to add new thermal mass," the authors write. "If your house sits over a crawl space or basement, you can still add thermal mass. Concrete floors can be attractive, durable, and easy to build.”

In fact, adding thermal mass during a remodeling project is rarely a good use of scarce budget dollars. And installing a concrete floor on top of an existing wood-framed floor is not an “easy to build” project.

Install a solar hot air collector?

The authors of No-Regrets Remodeling often fall into the “we have to be comprehensive” trap. This trap lures the authors into talking about every topic, including ones that deserve to be ignored.

“Active solar [space] heating — also known as solar thermal — requires a large solar collector, a pump, a large storage tank, and a distribution system,” the authors write. “Or you can use a collector that heats air, which is then blown into your heating-duct system.”

This is misleading. Homeowners should not consider installing solar hot air collectors — end of story.

Do ductless minisplit systems cost more than boilers with hydronic distribution?

No-Regrets Remodeling includes a table that lists the “relative purchase cost” for different types of heating systems.

In this table, the cost of a boiler paired with fin-tube baseboards units is deemed to be “medium,” while the cost of a ductless minisplit heat pump is deemed to be “high.” This seems backwards to me.

Warning! Don’t install a wood stove!

The paragraph on wood stoves is marked with a graphic warning sign — a red circle with an X in the middle. The implication: whatever you do, don’t install a wood stove.

Here are two of the reasons that the authors don’t like wood stoves: “If you can’t see the stove, you can’t feel the heat. … Woodstoves also present a significant fire hazard.”

The idea that you have to be able to see the stove to enjoy its heating effects is bizarre and untrue. For one thing, my sister-in-law Caryn is blind, and she can feel the heat.

For another, when the wood stove in my living room is putting out heat, I can feel the heat upstairs — even though I can’t see the wood stove.

Finally, a wood stove only presents “a significant fire hazard” if it is improperly installed.

A ductless minisplit for every bedroom?

The authors don’t particularly like ductless minisplit units. Here’s one reason why: “A separate indoor unit must be installed in each room.” Actually, that’s not really true.

Surprisingly, the authors advise, “Make sure that the installer commissions the control system [of the ductless minisplit] in both the heating and the cooling mode.” In fact, compared to other heating systems, ductless minisplits require less rather than more commissioningProcess of testing a home after a construction or renovation project to ensure that all of the home's systems are operating correctly and at maximum efficiency. .

Why is it so hard to write a book about energy?

I have a lot of respect for the people at the American Council for an Energy-Efficient Economy and Home Power magazine. They do good work, and they strive to share useful and accurate energy information with homeowners. For the most part, they succeed. Over the years, I’ve learned a lot from the publications of these two groups.

And yet, these two books, as good as they are, leave me profoundly disappointed. Homeowners are ill-served by books that contain as many errors as these two books. How do these mistakes happen?

The main explanation is that this field — saving energy in homes — is both complicated and evolving. It’s hard to know everything about the subject. Old advice is made obsolete by new research, and old product recommendations are made obsolete by new materials and equipment.

Warning: self-serving comment ahead

Compared to a book, a website like Green Building Advisor has many advantages. When I make a technical error, sharp-eyed readers are quick to set me straight, and in many cases, the error can be corrected the same day it is made. Publishers of books printed on paper can’t do this.

Even so, books that are re-issued and revised — emblazoned with “New second edition!” or “New tenth edition!” — should have fewer errors than these two books.

Martin Holladay’s previous blog: “Using a Tankless Water Heater for Space Heat.”

Click here to follow Martin Holladay on Twitter.

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May 8, 2015 6:09 PM ET

Martin, speaking of errors
by Eric Habegger

Martin, speaking of errors creeping into green subjects, I think you made one here. You said that "Of the three main types of ventilation systems — exhaust-only, supply-only, and balanced systems (HRVs and ERVs) — HRVs and ERVs have the lowest operating costs. The reason that they don’t make sense in mild climates has nothing to do with their operating costs; it has to do with the equipment’s high purchase and installation cost."

Not exactly. A Panasonic whisper green fan can operate as low as 3 or 4 watts in ventilation mode. While obviously not all houses are appropriate for ventilating with one or two bath fans, those houses that are appropriate and are in temperate climates have no equal in both low equipment costs AND low electrical usage costs. Do you know of an HRV or ERV that operates on 10 watts or less? In a temperate climate there just isn't enough of a temperature differential between in house temperatures and outside temperatures to overcome even the electrical usage difference.

May 8, 2015 8:40 PM ET

book idea
by norm farwell

How about Musings of an Energy Nerd, By Martin Holladay.
Whoop, I see it's already in the works --due out Nov 3.

May 9, 2015 5:32 AM ET

Edited May 9, 2015 5:35 AM ET.

Response to Eric Habegger
by Martin Holladay

You wrote, "In a temperate climate there just isn't enough of a temperature differential between in house temperatures and outside temperatures to overcome even the electrical usage difference [between a Panasonic fan in an exhaust-only system and an HRV]."

You're wrong, and I will cite two studies that examined the issue to back up my statement.

First of all, I will gladly stipulate that a Panasonic exhaust fan has a lower electrical draw than any HRV. However, when calculating the energy cost of a ventilation system, you have to consider (a) the electrical draw of the ventilating appliance, (b) the extra space heating energy required in winter, and cooling energy required in summer, to condition the makeup air.

Several researchers have performed these calculations. One of the first was Judy Roberson, whose calculations were made in a paper titled Ventilation Strategies for Energy-Efficient Production Homes. She compared the operating cost of an exhaust-only ventilation system to that of a balanced ventilation system with an HRV in four cities: Boston; Washington, DC; Houston; and Phoenix. In all of these cities, the operating cost of an HRV was significantly less than that of an exhaust-only system.

Similar calculations were also performed by John Semmelhack; I reported on his paper here on GBA, in an article called Are HRVs Cost-Effective? Semmelhack looked at the operating cost of ventilation systems in six cities: Atlanta; San Francisco; Charlottesville; Portland, OR; Chicago; and Burlington, VT. In all six cities, the operating cost of the HRV system was significantly less than the operating cost of the exhaust-only system.

I will post two images below that show the calculations. The upper image is Roberson's table (unfortunately, my screen grabber only caught 3/4 of the page; the link provided above will allow you to see the full table), and the lower image is Semmelhack's table.


Judy Roberson table.jpg Semmelhack HRV cost effectiveness table 1.jpg

May 9, 2015 5:40 AM ET

Response to Norm Farwell
by Martin Holladay

Yes, Taunton Press is preparing an anthology that will republish some of my blogs (along with additional introductory material and chapter introductions to tie it all together).

However, until you posted that link, I wasn't aware that Taunton Press and Amazon had already announced the book.

May 9, 2015 1:36 PM ET

Martin, thanks for the
by Eric Habegger

Martin, thanks for the information. I wasn't aware of this and it didn't match my intuition, which obviously was wrong. I think in cooling climates there is a wrinkle in this calculation though. If your climate is suitable for a whole house fan (not too humid in summer) one can time the air exhaust for the coolest hours in the night. That should have some impact on the annual cooling bill. Whether it's enough to offset the heating portion of the year is another question.

May 10, 2015 3:51 PM ET

Another book worth mentioning
by Jon Harrod

In this category, I really like Bruce Harley's "Cut Your Energy Bills Now." I think it does a good job of recommending homeowner-friendly measures and pointing out bigger opportunities that are usually better left to a professional. Out of the 150 tips there were only a handful I questioned, and I also thought that the overall balance between base load, envelope, and HVAC was pretty much right on.

May 11, 2015 4:34 AM ET

Edited May 11, 2015 4:37 AM ET.

Response to Jon Harrod
by Martin Holladay

I couldn't agree more. Bruce Harley is a Taunton Press author, a Vermonter, and a very smart guy. His advice is dependably good.

Taunton has published two of his books; both are authoritative and worth buying. Here is a link: Bruce Harley's books at the Taunton store.

May 13, 2015 12:48 PM ET

Good news
by Charlie Sullivan

Good news that Martin has a book in the works!

Dana, how is your book coming along?

And thanks for the pointer to Bruce Harley's books.

Jun 11, 2015 8:28 AM ET

Consumer Guide indeed dated
by Alex Wilson

Martin, thanks for your detailed review. I really wish that ACEEE would give me an opportunity to make revisions before new editions are issued. I've offered to do so in the past, but they haven't taken me up on the offer. It is indeed woefully out-of-date. If I, or someone else, really does a revision (instead of just adding a new cover), your input will be invaluable. I agree with most of your points—though not the point you always make that it doesn't do any good to install an outdoor air conditioner compressor in the shade. I just can't believe that carrying out the heat exchange with cooler outside air doesn't have some benefit.

Jun 11, 2015 8:39 AM ET

Edited Jun 11, 2015 9:06 AM ET.

Reply to Alex Wilson
by Martin Holladay

Thanks for your reply. As an author, I can appreciate the frustration resulting from your publisher's refusal to let you update an out-of-date book before it is reprinted in a "new" edition.

Concerning outdoor air temperature: The air on the shady side of a house isn't any cooler than the air on the sunny side of the house. If you use an ordinary glass-bulbed thermometer to read the air temperature, and the glass bulb is in the sun, it gives a false reading.

When you are standing in the sun and feeling hot, the feeling arises from solar radiation, not the air temperature. But all your air conditioner's condenser cares about is the air temperature.

When meteorologists report that the outdoor air temperature is 80 degrees F, that means it is 80 degrees everywhere. Small variations in air temperature directly adjacent to the siding of a house are irrelevant, because the volumes of air where these microclimates occur are tiny.

Jun 11, 2015 9:59 AM ET

Hard to imagine it doesn't matter at all
by Charlie Sullivan

When the compressor is running and pulling huge volumes of air through its condenser, it is circulating enough air that local pockets of warm air probably don't matter. But I could see two cases in which it would matter.

One is that on moderate days when the A/C doesn't kick on until 2 or 3 PM, the noon sun will warm case of the compressor and warm up the whole thermal mass of the metal in it. Then when it starts up it is at a disadvantage relative to a unit that started out cooler. I haven't done the analysis to see whether that would be significant.

The other would be a case in which one side of the house has a large wooded shady area, which the other side is open, and perhaps near lots of asphalt. The wooded area could truly have cooler air, both because of shade and because of evaporative cooling. For example, this report gives examples on different spatial scales, including

"a cooling band of 1–2 °C extended some 20 m around a small (60 m by 40 m; 0.24 ha) greenspace in Kumamoto City, Japan (Saito, 1990–91)"

And from the reference cited the air temperature inside the 60 x 40 m area was 2.5 to 3 C lower than in the surrounding region.

Jun 11, 2015 10:33 AM ET

Response to Charlie Sullivan
by Martin Holladay

I agree with your first sentence, which sums up the correct answer to this puzzler: "When the compressor is running and pulling huge volumes of air through its condenser, it is circulating enough air that local pockets of warm air probably don't matter."

The way that heat is removed from the outdoor coil is that large volumes of air are blown past the coil, transferring the heat from the coil to the moving air (as I'm sure you know). While solar radiation can, indeed, heat up the metal jacket surrounding the condenser, the temperature of this metal jacket won't be high enough to significantly change the temperature of the large volumes of moving air.

Concerning your hypothetical example #2 -- the example from Japan -- count me a skeptic. I seriously doubt that there are many houses with night-and-day microclimates on opposite sides of the house.

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