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HRV, ERV

Air-change ventilation units are the devices, which take stale air out of your home and bring inside the fresh one so you should not rely on cold air drafts to allow of fresh air to the house. They look like a box, which consist of 2 fans. In a few of the warm spots of Canada, these units are legitimate systems on their own. Majority of people in Canada have troubles with distributing of the very cold fresh air, and waste a lot of costs throwing the hot air directly outside, so we have taken these air change systems on arms.

HR and ER Ventilation

tAn air-to-air heat exchanger is more known today as a HRV (Heat Recovery Ventilator). It is an air change central ventilation appliance, which exhausts stale air outside the house and brings in an equal amount of fresh air to replace it while stealing the heat from the outgoing air to warm up the incoming air.  It provides the proper changes of air in your home to control of humidity and pollution automatically and it frequently needs little or no pre-heating of the incoming cold fresh air. Additionally to this family of ventilation devices is the ERV (Energy Recovery Ventilator). This unit does the same working process as the other devices but has a special design so it can return some of the moisture back into your home, saving even more amounts of energy while not drying out the home as much as the heat recovery ventilator. Over drying was discovered to be a problem in smaller buildings with the HRV’s where-as in larger buildings with problems of moisture the ERV would not be suitable.

If we look at the situation from a strictly cost payback point, unless you have a fairly well-sealed house, the heat saved does not justify the capital and operating paying bills. In a poorly sealed home the system can be detrimental, as it can over-dry an already dry home and further complicate the strange and variable air currents in drafty old homes, possibly aggravating moisture problems inside the walls. As well, you are only recuperating heat from a small portion of the ventilation of whole home when most of the air changes is done by the cold drafts of air.

yAs soon as your home is reasonably sealed, also, you should better install an ERV or an HRV as the major step to an energy-efficient and healthy home. We do not recommend to built a new home without one. These devices protect your home from damage of moisture with the help of ventilation in a proper way and provide you with comfortable fresh air spread throughout the home. In a very well sealed building, such units become not only cost effective but almost required to keep the good quality of air. We can compare it with the watering of your lawn; if there are many rains, the lawn sprinkler is not used, and could even cause a flood. But if the sky falls rarely, the sprinkler becomes more valuable — and with no rain at all, you can not live without the unit.

Today on the Canadian market there are 3 main designs of home air-to-air heat exchangers: parallel plate cross flow, parallel plate counter flow, and the capillary wheel rotary design. (Some low quality central exhaust ventilation system manufacturers, which specialize in marketing of high pressure have tacked on what is called a heat-pipe exchanger, two pipes, one inside the other. Commercial heat pipe exchangers are available, but the ones offered for houses appear to be more of a gimmick designed to fool people into thinking that they will save significant energy with this unit. There is not laboratory information, which shows that a few feet of double ducting exchanges much heat.)

Today all the devices have about the same price, if you are looking for units of the same size and efficiency of heat recuperation. The best installation is with rigid ducting, not flex one, because it only provides better flow of air, but have the higher price of material and labor.

With all of these devices, the slower the fan speed, the more efficiently they exchange the heat so they will be doing their best at slow continuous speeds. Because you must regularly remove and clean the core, you have to be insured, that you can do it easily. You should not install these devices in the attic, because nobody would like to go there to do the cleaning of the core (we also remember about them the trouble of everything freezing up). Of the parallel plate types, the counter-flow design (cold and hot flow of air in opposite locations) has higher efficiency but is much more difficult to design and use than the one of the cross-flow design (cold and hot flow of air in the same location or at right angles to each other).

It does not matters what type you will change, but you should remember to insist on the following features:

  • Continuous minimum operation should be from 100 to 200 cfm (higher speed humidistat or manual over-ride is a good variant).
  • Defrosting should be automatic.
  • Cleaning should be easy and quick.

Features Of Fresh Air Ducts:

  • it can be run into the cold air plenum of your furnace if you have a forced air furnace (you must run the furnace fan on continuous mode), to turn the temperature of air up to room temperature and mix it with household air, which already exists
  • or, if the fresh air is ducted directly into the rooms, you have to place the outlets high up on the wall and direct them across the ceiling where the cold fresh air will mix with excess ceiling heat.
  • it could play the role of your furnace itself if your home is insulated on the high level (low heating demand) with the help of installing an electric plenum heater in the fresh-air distribution ducting (and electricity does not have a high price in your location).

Features Of The Stale Air Ducts – They Should:

  • udraw from high activity places around your home.
  • draw from bathrooms.
  • not draw from the clothes dryers. Year of attempts showed that it always has blocked system with the lint as a result. We recommend you to duct your clothes dryers directly outside your house.
  • draw from kitchens but should not draw from ranged hoods because grease filters are just not good enough to keep the cleanliness of ducts. The kitchen air will be fresh and the exchanger will be relatively grease-free with the help of non-ventilated filter hood over the range and an HRV stale-air grill on an opposing wall. Many people install an ordinary range hood exhaust, whcih shoots outside since it is rarely used anyway. 

The best installation of your new system of ventilation will have a fresh air input and/or an exhaust output in every place of your home – there will be no room, which is collecting stale air.