Tags: water

15 Jul 2009, Comments Off

Tank, Tankless or Thankless

Author: admin

Is going “tankless” as liberating as it sounds? Is owning a tankless water heater a solid indication that you’re saving money while reducing environmental damage?

Your answer to these questions may depend on whether you own or are buying a newly-constructed home versus living in or purchasing an existing, decades-old property.

Conventional water heaters heat litres of stored water which is kept hot 24/7, even when there is no demand. Tankless units are heaters which heat water on demand, then stop.

First of all, don’t get sanctimonious if your tankless water heater was part of the features of the new home you bought or had built. Starting from scratch and incorporating energy-efficient, environmentally-friendly systems during construction is always easier, and usually less expensive, than retrofitting, or adding a modern system to an older home.

The benefits and cost-considerations of tankless water heaters in new homes can make this installation a feasible if not a preferred alternative to conventional tank-style heaters. New home construction standards are normally higher than those that existed for homes built in the last century or earlier. New plumbing, electrical, sound-proofing and other systems favour optimum installation and operation of tankless water heaters and other modern technologies.

If you own or want to buy an existing property, your commitment to reducing “your footprint” and saving energy may not be enough to make tankless water heaters the right way to achieve your environmental and financial goals. You can still have an energy-efficient, green home with a conventional water heater, but you’ll just have to go about it differently.

One of the most important lessons to learn about the current rush toward “green” is that there are just as many inappropriate applications of good ideas and over-sold environmental or energy-efficient solutions as there are “right fits.”

Don Fugler, Senior Researcher in Policy and Research at Canada’s national housing agency, Canada Mortgage and Housing Corporation (CMHC), is currently managing CMHC’s initial tankless field project designed to determine the actual savings gained when converting from a well-functioning conventional water heater to a tankless unit.

“Basically, what we hear is that tankless water heaters do save energy in a lot of cases, but what is not necessarily established so far, is what people should expect,” said Fugler. “It is probably different from the theoretical savings–that you just calculate based on efficiencies. What house usage is unlikely to get significant savings? The fact [is] that water heater usage or homeowner draws on hot water are a lot different in reality than they are modelled in standards. This makes a difference because the way they are modelled in standards actually benefits tankless water heaters. I don’t think they set it up this way, it just does.”

Tankless water heaters are not a new idea, just relatively new to Canadians. In retrofit situations, they may not always be practical, cost-effective or feasible. Fugler offered a few issues to consider in evaluating whether tankless is right for you:

  • Net result may not be a gain “Part of the problem, or part of the solution, is tank heaters lose their heat to the house….So even though a conventional water heater does lose heat, it is seen to be heating your house and that is an asset for two thirds of the year…. In Canada, which is more a heating than a cooling climate, tankless is only going to have a third of the advantage that it may have in a cooling climate.” Fugler explains that expected savings from converting to tankless may not materialize because, while fuel consumption by the water heater may go down, fuel consumption to replace heat to the house may increase. This has been found for shifts to high-efficiency furnace fans and CFL light bulbs.
  • Billing disappointment The quoted percent of savings should be applied to the portin of the gas or electric bill represented by the water heater. With all the charges piled confusingly on a gas bill, an absolute savings may not be visible. If you expect to save significant amounts, you may be disappointed.
  • Pay back clarity For the two reasons above, the quoted pay back time may be hard to calculate or much longer than stated. Sales representations would normally include best case scenarios. Where hot water bills are high, savings could be more noticeable. With low or conservationist usage, the savings may be small and the pay back much longer.
  • Hot water delivery How long does it take hot water to arrive at the tap? Since home designs usually locate heaters in an otherwise unused corner of the basement, second-floor and higher bathrooms may be a long way off. Having to run water as long as 5 minutes to get the hot may result in wasted water. Low-flow shower heads increase delivery time. Anti-scald valves like those required in new homes may also interfere with hot water availability. Recirculation pumps may help this problem, but that’s another cost to consider.
  • Heating differential Municipal water may be very cold, requiring considerable fuel to heat it to the desired temperature. Drain water heat recovery installations recycle hot wastewater to heat up incoming cold water to warm by spiralling the wastewater piping around the intake pipe. However, this approach is only practical for those who regularly take long hot showers, not baths.
  • Flow limits and use patterns Tankless heaters have minimum flow limits, so they don’t heat water for small draws like rinsing your hands. Some users turn on a second tap to reach the flow threshold for hot water at the tap where they want low flow hot water. It is this type of water-waste pattern and other use changes that are of interest to Fugler in the current research project. To achieve maximum desired flow, particularly to have two or more simultaneous uses with lots of hot water, intake pipes may need to be increased to 3/4 inch from the conventional inch. In large, high-usage homes, more than one unit may be advisable.
  • Adequate fuel supply Gas supply input may need increasing to 3/4 inch pipe to achieve desired hot water flow. A comparable cost may be required to upgrade to a larger service panel for an electric tankless unit.
  • Venting and noise The exhaust gases and moisture from gas tankless water heaters are vented outside, not into a chimney, in a manner dictated by bylaws and codes. Proximity to neighbours may cause complaints about noise and condensation, or it may make the installation impossible. Decks and patios may also restrict venting choices. More expensive and higher efficiency condensing units may offer more venting flexibility, but installation costs may increase. If venting is not possible, an electric unit may be the only tankless alternative.

Tankless water heaters are expensive to purchase and installation in Canada. Fugler predicts that these and other issues will be resolved through technological advances and government regulation. Tankless water heaters will become the new normal in the decades ahead.

For now, invest in knowledge in advance of a purchase, or regret in hindsight…your choice. Don’t rely on salespeople or installers to make decisions for you. Buyer beware is the law. Buyer be aware is the solution.

http://www.homes101.net/news/n4655

brought by Moishe Alexander, CFC  Canadian Funding Corp CEO

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Window Installations – Achieving field performance

Author: admin

With proper design and clear specifications, it only remains to confirm that the window is installed properly in the field to make certain that the desired performance is achieved.
First, try to make sure that the windows on site are the ones that were specified. Check window labels (see Figure 4), invoices or shipment waybills for the model and manufacturer, and glazing options. Low-e coatings are impossible to verify just by looking at them, but there are ways to determine whether a window has a low-e coating (even if it is not possible to verify that it is the exact coating that was specified). A commercially available, handheld electronic device can be used to determine if a low-e coating exists and on which surface.
For a low-tech version of the same verification, use a flashlight, butane lighter or other source of light. With the light source held at the correct angle, a reflection of the light source from each surface will be visible. If there are no low-e coatings, the images will be similar, but if a low-e coating exists, the reflection of the light source off that surface will be different.
A low-e coating reduces the amount of energy transmitted in the long-wave part of the spectrum, so more of those wavelengths will be reflected back toward the viewed and the image will appear redder than the others. A black surface behind the window makes viewing easier.
Once the product has been verified as being what was intended, several field tests can verify the performance of the installed product. These include noise transmission, air leakage, ease of operation and water leakage.

Noise transmission

ASTM E966 is the field version of the STC lab test. A decibel meter and calibrated sound source are required. Several measurements are taken from the interior and the exterior, with the decibel reduction computed and converted to an STC rating as per the Standard. The specifications should indicate acceptable levels, recognizing that the fieldmeasured STC will not meet the same level of performance as the lab-rated specimen.
The tests should include the wall-window interface when performed in situ. This will not confirm the window rating, but will demonstrate the actual performance.

Air leakage

Portable air-leakage test units are commercially available. These units contain a vacuumcleaner motor and a calibrated airflow meter. The user must create a chamber to isolate the specimen of interest — this can be a window, or a bank of windows, or some other assembly. The test can isolate the window, or include the wall-window interface, depending on how the chamber is sealed to the wall.
Air leakage required to maintain a pressure difference is measured through the airflow meter. The result can be displayed as a flow (L/s or m3/hr) or a flow per unit area (L/s/m2 or m3/hr/m2, which is more common in door testing), or in the A440 units of m3/hr per metre of crack length. This can then be compared to the A rating, remembering that the field measurement will probably be higher than the lab-rated specimen.
If a small amount of smoke from a smoke pencil can be applied at the exterior, it may be possible to identify leaks, but this is usually easier to do with a blower-door test. The smoke pencil can be used to visualize the locations of leaks, which can then be addressed as needed.

Ease of operation

This parameter is a concern for elderly or physically challenged occupants. The window can be tested by applying a simple spring balance to the operating hardware.
The amount of force required to initiate motion, and to maintain motion, is measured, and must be less than the levels set in the A440 Standard. The Standard also defines where to take the measurements, depending on the window operator type. Ideally, let the occupants try the windows as a supplement to the test measurements.
Often they can give you useful feedback as to the required angle of applied force, as well as the amount of force necessary to open, close or lock the window. Note that ease of operation is usually a contrary requirement to air leakage and water leakage, both of which require the window to be tightly sealed (and therefore, usually difficult to operate). Proper selection of operating hardware can address these conflicts, but the best test occurs on the installed window.

Water leakage

Resistance to wind-driven rain is a particular concern in coastal locations, but water leakage is not welcome anywhere. Thus, installed windows should be properly evaluated in this regard.
The ASTM E1105 Standard is a field version of the E 547 test, used to determine the A440 B rating. Water is uniformly sprayed on the outside of the window at a specified rate and the window is subjected to an air-pressure difference to simulate wind pressures. The pressure is cycled in an attempt to simulate gust loading: A440 requires four cycles of five minutes with pressure “on” and one minute with pressure “off,” while the water spray is continuous throughout the test. The A440.1 User’s Guide gives test air pressures.
These pressures are maintained for the four “on” cycles, so air pressure should be continuously monitored. Before testing, the window should be preconditioned. As defined in E1105, this means opening, closing and locking the window five times, to ensure that the hardware is working and the seals are not over-tightened (which would affect the ease of operation).
The window should be observed carefully for signs of leakage. A clear chamber for testing, made of either polycarbonate or acrylic sheets, will facilitate the review. Note that there is a difference between the A440 pass-fail criteria and that of the E1105 procedure.

A440 defines water leakage as:

water penetrating the window assembly and wetting interior room surfaces;
water passing through the window into the wall below the sill;
OR
water trapped in the window assembly after the test pressure is released.

Any of these three occurrences constitutes a failure under A440. The E1105 procedure only considers the first of these to be a failure, and does not mention the other two modes of failure. It is important to define pass-fail criteria BEFORE the test begins, ideally in the project specifications.
Also, the last of these criteria is somewhat subjective: if the water is still in the assembly, but the weepholes and drainage are clearly working (so that the water will eventually drain out of the assembly), this could be considered a “Pass,” even though water in the assembly after the last oneminute “off ” cycle is, strictly speaking, considered a “Fail.”
Note that the E1105 test equipment must be calibrated, and the calibration is to be repeated every six months to make sure the water spray is constant. Reviewed by Guiseppe Strazzeri.

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Window Installations – Shiplapping to shed water

Author: admin

Sheathing membranes, whether polymer or paper based, should be applied as shiplaps to direct water down and away from inner wall assembly. Sheathing membranes at the jamb should overlap the upstands of the impermeable membrane at the sill location.
At the head of the window, sheathing membranes should overlap window flanges and head flashings. Reviewed by Martin Lapedus.

Tags

AIR Alexander Building Canada Canadian Funding Corp. Canadian Funding Corporation CFC cmhc construction Design IDP integrated design Moishe Alexander performance report Reviews Window Window Installation
  •