Six Steps to Success With Heat-Recovery Ventilation

first_imgThis post originally was published at the Zero Energy Project and is used here with permission. Ventilation is essential in all modern homes. When homes are built with energy efficiency in mind, they are more tightly air sealed than the average building and therefore need fresh air distributed through the entire home. A central ventilation system exhausts stale indoor air from high-moisture areas, such as bathrooms and kitchens, while simultaneously supplying fresh air to living areas and bedrooms. Central ventilation also offers the option of filtering the outside air to remove particulates, allergens, and chemical pollutants. The result is well-distributed fresh clean air.All homes pay an energy penalty for ventilation, because air that sneaks in through cracks and openings must be heated or cooled. Very airtight construction combined with central ventilation systems offer the opportunity to preheat incoming air in winter by transferring warmth from the stream of outgoing air. A heat exchanger can capture between 70% and 95% of that heat to reduce the energy needed to heat incoming air – something that is especially valuable in colder climates. 1. Calculate required air flowThe amount of fresh air flow for any type of ventilation system is calculated according to a national standard known as ASHRAE 62.2 – 2010, which takes into account both the number of occupants and the conditioned floor area of the home. The simple equation goes like this:(Occupants x 7.5) + (square feet of conditioned floor area x 0.1) = ventilation rate in cfmSo, four people living in a 2,000-square-foot home would need a continuous air flow of:(4 x 7.5) + (2000 x 0.01) = 50 cfmThis formula will get you close enough, but if you want to be even more precise, there is a sophisticated online calculator that allows detailed inputs for more exact results. HRV or ERV?Are HRVs Cost-Effective?Does a Home with an HRV Also Need Bath Fans? Designing a Good Ventilation System Green Basics: Ventilation Choices: Three Ways to Keep Indoor Air Fresh While most HRV equipment is well-designed and durable, the technology has been plagued by poor installation practices that reduce their value. “In all my many years in the HVAC industry,” says Bruce Manclark of CLEAResult, “I have never seen anything screwed up as much as HRVs.” Here are the six steps to success for selecting and installing HRVs. 2. Select efficient equipmentHRVs have internal fans that run many hours a day and sometimes continuously. You should choose a model that provides the necessary air flow while sipping as little energy as possible. HRVs should be tested and certified by the Heating and Ventilating Institute. Most manufacturers show these testing results in their product literature. A great way to compare products is the online version of HVI’s Certified Products Directory.To choose an efficient model, first find the sensible recovery efficiency (SRE) column in the HVI directory. This shows how efficiently the unit transfers heat between air streams. Look for an SRE of at least 80%. This value is clearly shown in the database. Next, you’ll need to calculate how efficiently the unit moves air. This is called efficacy and is expressed as cfm per watt. While this number does not appear in the database, you can easily calculate it by dividing Net Airflow (cfm) by the Power Consumed (watts). You want the efficacy to be at least 1.25 cfm per watt. 6. Decide on an HRV or ERVThe information above applies to both HRVs and ERVs, which may perform equally well in most climate zones. But what is the difference between a heat recovery ventilator (HRV) and and energy recovery ventilator (ERV)? The main difference is that an HRV transfers only the temperature of air between the outgoing and incoming air streams. Engineers call this sensible heat. It’s the heat you feel directly as a change in air temperature.But air always contains some water vapor and that vapor also holds energy. ERVs transfer sensible heat plus a substantial amount of water vapor between the incoming and outgoing air streams along with the energy in that vapor, a property called enthalpy. Because ERVs capture this additional form of energy, their efficiency ratings are generally higher than HRVs.But wait! Isn’t the purpose of ventilation to remove humidity from a home? Why have a device that returns some of the water vapor? Some climates are very dry and will benefit from this feature of an ERV. This can be useful in many inland areas of the American West. In the American Southeast, the situation is reversed, but an ERV is still appropriate. Here, the indoor air has been dehumidified, so ventilation would introduce outside air with a much higher relative humidity. In this case, the ERV expels the humidity back to the outside and helps maintain a lower indoor humidity.These two examples may seem contradictory. In one case, humidity is maintained inside the home and, in the other case, humidity is expelled. However, in both cases, the water vapor jumps across the core, from the more humid air stream to the less humid air stream and returns to where it came from originally. Consistent with basic physics, the water vapor moves from a higher concentration to a lower concentration.If you follow these six steps to selecting the right equipment, you’ll be on the right track to achieving better indoor air quality and greater energy efficiency. For more details see the HRV System Best Practices Poster at BetterBuiltNW.com.center_img 4. Locate fresh air supply pointsIn order to mix fresh air throughout the house, supply points should be positioned a considerable distance from the exhaust points. Bedrooms and living rooms are good choices. Even though incoming fresh air has been tempered by the heat exchanger, during the winter the fresh air is usually slightly below room temperature, so take care not to make occupants uncomfortable by blowing that air directly onto them. Place the incoming vents high on a wall, so it will mix with warm air and not be noticed. In a bedroom, introducing fresh air into a closet allows gentle mixing with room air. Plus, it has the added benefit of helping keep the clothes smelling fresh and clean! RELATED ARTICLES 5. Create a dedicated duct systemMost experts agree that it’s best for an HRV to have its own dedicated duct system. If the home has hydronic heat or ductless heat pumps, that’s the only choice. In this case, the HRV mixes the air throughout the house. However, homes with forced air heating and cooling systems can share the ducts used for heating and cooling. This saves money on material and labor and offers great distribution of fresh air. Integrating HRVs with forced air systems requires careful planning, proper controls, and sound installation practices. Manclark covers these issues in detail below. Heat-recovery ventilators (HRVs) and energy-recovery ventilators (ERVs) remove stale air from the home and replace it (in winter) with preheated fresh air from outside. The result is better indoor air quality and lower energy use than in standard homes. The HRV itself is fairly simple: an airtight box with a heat exchange core that transfers heat from the indoor air to outside air (or vice-versa) as the air passes through the box. The box also contains two small fans to move the air. All the points below apply equally to HRVs and their close cousins, energy-recovery ventilators (ERVs). This article is based on training developed by Bruce Manclark and Dan Wildenhaus of CLEAResult. This is the first of two parts. Part 2 will cover integrating HRVs with forced air heating and cooling systems. 3. Locate exhaust pointsSince the idea is to remove humid, odiferous air from the house, locate the stale air exhaust points in each bathroom, kitchen, utility room, and other high moisture areas. This allows heat recovery from areas of the home where humidity and odors are most abundant. The HRV can replace spot ventilation (exhaust) fans in these rooms to save money and provide a more pleasant environment. If homeowners are fond of a steamy shower, but averse to a foggy mirror, a standard bath fan can be installed to supplement the HRV.An exhaust point located near the kitchen area should be at least six feet from the cooking surface. This exhaust point is intended to remove general moisture and cooking odors. While HRVs are not intended to entirely replace the range hood, in some applications, with an HRV in the kitchen, it may be possible to eliminate the external venting on a range hood and operate it in recirculation mode only. As with bathroom spot ventilation, occupant habits may dictate a standard range hood in the kitchen to expel moisture and odors.last_img read more

Patnaik flays Centre for stopping welfare schemes

first_imgAs rich tributes were paid to Biju Patnaik on his 101st birth anniversary of Sunday, Odisha Chief Minister Naveen Patnaik criticised the Narendra Modi government at the Centre for stopping many welfare programmes ignoring the interests of the people living in tribal and backward regions of the State.The State government, however, continues to implement those schemes using its own resources to safeguard the interest of the people, and would continue to do so, said Mr. Patnaik said while addressing a gathering at the Biju Janata Dal headquarters here.Progress in many sectorsWhether one admits or not due to political reasons, but the State has achieved significant progress in various sectors since the BJD started ruling the State in 2000, said Mr. Patnaik. “There is a huge difference between Odisha of 2000 and today’s Odisha,” he said.Besides faring better than the national average in infant mortality rate, Odisha has also seen infrastructure development, investment flow, growth in employment opportunities and increase in food production and people’s income, said Mr. Patnaik. Stating that the BJD has remained No. 1 in the recently held panchayat elections and will remain in the same position in future, Mr. Patnaik urged the gathering of party leaders and workers to stay in touch with the people. Observing that BJD doesn’t believe in slogans, but in service, the Chief Minister called upon his party workers to continue on the path shown by Biju Patnaik to serve Odisha.Birth centenaryMr. Patnaik also attended a function organised at port town of Paradip to mark the closing of the year-long Biju Patnaik birth centenary celebrations. He also flagged off a mini-marathon in Bhubaneswar to mark the occasion.The Chief Minister also highlighted his government’s achievements at a function organised to mark the celebration of the Panchayati Raj Day which is observed on the occasion Biju Patnaik’s birth anniversary every year.last_img read more

Supreme Court stays Bombay High Court order to file FIR against Dhananjay Munde

first_imgThe Supreme Court on Friday stayed a Bombay High Court order directing registration of a First Information Report against Maharashtra MLC and NCP leader Dhananjay Munde in an alleged illegal purchase of government land case.A Vacation Bench of Justices Ajay Rastogi and Surya Kant also issued notices to the Maharashtra government and the complainant in the case, Rajabhau Phad.During the hearing, the Bench queried, “what was the exceptional feature in the case” that led the High Court to order the registration of the FIR.In his petition, Mr. Munde, sought stay of the High Court order that directed the police to file a case against him for allegedly grabbing land at Pus village, Ambajogai taluk, Beed district belonging to government.The top court, however, declined to go into the merits of the case as of now.Earlier in the morning, the Beed police lodged a case of cheating and forgery against Mr. Dhananjay Munde and 14 others in the case.An FIR under Sections 420 (cheating), 465 (forgery), 468 (forgery for the purpose of cheating), 464 (false document) and 471 (using as genuine a forged document) of the Indian Penal Code (IPC) was lodged against Mr. Munde and the others at the Bardapur police station.The police action follows a June 11 order of the Aurangabad Bench of the Bombay High Court, directing an FIR to be registered against Mr. Munde, who is Leader of Opposition (LoP) in the Maharashtra Legislative Council (MLC), within four days of the court order.The court had passed the directive on a petition filed by Mr. Phad, who had accused the NCP leader of illegally purchasing land for his Jagmitra sugar factory in Beed district.According to Mr. Phad’s petition, the disputed plot of land at Pus village in Beed’s Ambejogai tehsil belonged to the State government and was given to the Belkhandi Math in Beed as a ‘gift’ to its chief priest or mahant, Ranit Giri.In 2012, Mr. Munde had purchased the 17-acre plot from Mr. Giri’s heirs by applying for non-agricultural status of the land.The petitioner had challenged the purchase, stating that as the land originally belonged to the government, it could not be sold to anybody.Stressing that the land for the Jagmitra Sugar Mills was purchased “in strict accordance to rules,” Mr. Munde has refuted the allegations against him, stating that “misleading information” was presented against him in the court.He has alleged that Mr. Phad’s complaint against him smacked of “political vendetta.”The NCP leader said that Mr. Phad, who is the son-in-law of scam-tainted businessman Ratnakar Gutte, was attempting to frame him as he had exposed the farm loan fraud allegedly committed by Mr. Gutte, a prominent sugar baron from the Marathwada region considered to be close to the ruling Bharatiya Janata Party.Mr. Munde’s lawyers have said that there was no mention of the land belonging to the government at the time of the purchase in 2012.This is not the first time the NCP leader has found himself in a soup over shadowy dealings.In October 2013, the Beed District Central Co-operative Bank had lodged a complaint pertaining to fraudulent behaviour against Mr. Munde and 15 others at the Parli police station in Beed.The BDCC had alleged Mr. Munde, as chairman and director of the Parli-based Jagmitra Co-operative Cotton Ginning and Pressing Mill, had taken loans from the bank amounting to ₹11.79 crore between 2003 and 2011 and had failed to repay them. Despite the lodging of an FIR and the filing of a charge sheet against the NCP leader, a local court had stayed Mr. Munde’s arrest.last_img read more