Tags: heat

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

17 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: GUIDELINES FOR DELIVERING EFFECTIVE AIR BARRIER SYSTEMS-INTRODUCTION

Author: admin

INTRODUCTION

Inadequate control of airflow through the building envelope is often a primary factor contributing to premature building envelope failures. If moisture-laden air is permitted to travel through the building envelope, the moisture may, under certain environmental conditions, condense within the walls of the structure. In above-freezing conditions, this may cause corrosion or rotting of the structural components, staining of the interior and/or exterior facade, and may stimulate the growth of mold and mildew. In cold climates, accumulated moisture may experience numerous freeze-thaw cycles, which can precipitate spalling and the formation of icicles on the exterior facade.

Air leakage is also a concern in areas where interior temperatures differ greatly from exterior temperatures, such as the Prairie Provinces, which can experience periods of extreme cold during the winter and extreme heat during the summer. The excessive heating and cooling loads placed upon buildings in this type of climate leads not only to an increase in space conditioning costs to the owner, but also has a negative impact upon the environment through increased energy consumption and the emission of greenhouse gases. In fact, studies conducted on high-rise residential and commercial buildings in cold climates have shown that anywhere from 20 to 50 percent of heat loss can be attributed to air leakage.

In Canada, building rehabilitation for roofing and wall system repairs and replacement cost an estimated $7.5 billion annually. A conservative estimate of the premature failure rate is 3 to 5 percent, or $225 to $375 million per year, with premature failure defined as any performance condition requiring repair or replacement of the system before the benchmark date. The building envelope has been identified as being particularly vulnerable to durability problems.
It is the growing global awareness of these air leakage-related problems that is driving the federal governments in Canada and the United States to introduce more stringent codes and regulations to govern building air permeance. In order to improve occupant health and safety, revisions were made to the National Building Code of Canada (NBCC) in 1995 designed to reduce air leakage in buildings, including those buildings classified within Part 3 of the Code1. Public Works Canada also recently revised their National Master Specification to include air barrier inspection and testing. In the United States, Persily’s Envelope Design Guidelines for Federal Office Buildings: Thermal Integrity and Airtightness (1993) also documents the requirements as outlined in the NBCC. In addition, State Energy Codes are being adopted and/or revised, making air barriers a mandatory requirement in new construction and retrofits. ASHRAE/IENSA Energy Standard for Buildings Except Low-Rise Residential Buildings (90.1-1999) also governs building envelope sealing.
Recently, air barrier trade associations have formed in Canada and the United States with the objective to improve the quality of air barrier system installations by providing education and training for the workforce. For an installer to become ‘certified’ through the association, an applicant must possess the required knowledge of air barrier material and system theory, and demonstrate sufficient skills in practical applications. In addition, through the associations’ quality assurance programs, documented self-testing and on-site third party audits are performed to verify the quality of the installation, and confirm the certified installers’ ability to build to expected standards.

While there are numerous ASTM (American Society for Testing and Materials) methods, says Jan Luistermans, for testing air barrier systems and/or components, there is no generic regimen for the application of these techniques being utilized on a widespread basis. The need for a complete design, inspection and testing protocol for air barrier systems cannot be understated. A recent study concluded that even routine testing can have a significant impact upon the airtightness of a building. Where air leakage testing was conducted, there was an overall reduction in air leakage for the system, a significant decrease in heating and cooling loads, a reduction in greenhouse gas emissions, and an increase in the life cycle of the building envelope.
With the growing use of inaccessible air barrier systems (such as bituminous membranes), on-site inspection and testing during installation is necessary to identify problems before the system is covered with finishing materials. The cost to repair an air barrier system after it has been covered can be conservatively estimated to be 50-60 times the cost of a correct first-time installation. Hence, the need for inspection and testing is obvious.

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Window Installations – Number of glazing layers

Author: admin

Most building codes do not permit singleglazed windows in small (“Part 9”) buildings because of the potential for condensationrelated problems. The glazing options are therefore limited to a minimum of double glazing, with an IGU providing the most common form of glazing system.
An IGU can comprise many layers, although practical considerations limit the maximum to four. Multiple layers reduce heat loss not because of the additional glass (glass is in fact a good conductor of heat) but because of the additional layers of insulating air trapped by the glass. Double-glazed windows (two layers) are most common, but triple glazings are now more common in certain areas, such as Manitoba. A double-glazed window with a storm panel is effectively a triple-glazed system, and is usually treated as such.
Quadruple-glazed IGUs are rare, but becoming more common, especially with the introduction of thin plastic films instead of glass layers. A window with four layers of glass is heavy, and difficult to move, install and operate. On the other hand, a window with two glass layers and two films weighs about the same as a double-glazed window, yet provides the performance of quadruple glazing. Reviewed by Moishe Alexander.

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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
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