The state of MN has been at the forefront of adopting residential building codes that incorporate energy efficiency designs for residential mechanical ventilation. These codes have additional provisions which address some of the serious side effects such designs can have on the home’s inhabitants and structural integrity.
Back in the early 1980’s, these energy efficient building designs introduced highly insulated air tight homes. These designs significantly reduce a home’s energy consumption but created adverse consequences that could not go ignored. Extensive research conducted over the past 30+ years was the driving force behind the current 2015 Minnesota Energy Code. Considered controversial by the builders and realtors, primarily due to the code’s cost impact on a home’s sale price, this code is also viewed as a showcase for all the advocates of the advancement of building science.
In the past, many residential ventilation systems were either unbalanced or exhaust only; typically, exhausting more air than was brought into a home. This approach was generally considered “easier” and” less costly.” The state of MN however, decided that the benefits of a balanced ventilation system far outweighed any cost concerns.
The 2015 MN Residential Energy Code requires a total ventilation rate based on the total square footage and the number of bedrooms there are in a home. A minimum of 50% of the total ventilation rate must be met by a continuous and balanced whole-house mechanical ventilation system. Kitchen and bath fans can be a part of the overall ventilation system, but an HRV/ERV system alone can meet both the total and continuous requirements of the current code. Such multi-purpose systems use minimal amounts of energy, are energy efficient (many models are Energy Star rated) and improve the indoor air quality of a home.
New homes already adhere to the 2015 MN Residential Energy Code. Builders are now required to install these ventilation systems during construction, but homeowners can retrofit older homes with an HRV/ERV system also. Though it is not required to add a balanced system to homes built before February 14, 2015, it is a relatively simple modification that connects to a home’s furnace ductwork to simultaneously exhaust indoor air and bring in outdoor air.
An unbalanced mechanical ventilation system involves fans exhausting and/or supplying air in unequal amounts into a home. When the supply air exceeds exhaust air, it creates positive pressure in a home. When exhaust air exceeds supply air, it creates negative pressure. Homes operating under positive and negative pressures can affect the safe operation of fossil fuel appliances and expose a home’s inhabitants to serious health risks over time; toxic gasses and airborne contaminants such as radon, mold, allergens, bacteria and viruses. A balanced ventilation system in homes negates pressure differential consequences and helps minimizes the impact of such health risks by effectively diluting their concentrations in an efficient manner.
Negative pressure can cause back drafting, a likely reason why your fireplace doesn’t draft very well. Large exhaust devices such as kitchen range hoods (generally over 300 cfm) pull significant amounts of air out of a house, your fireplace chimney (when open) will be trying to bring air back into the structure to reach a point of pressure equilibrium. To remedy such situations, a make-up air device can be installed which is capable of mechanically bringing back into a home the same amount of air that’s being exhausted by the range hood. Make-up air requirements are also a part of the 2015 MN Energy Code.
The movement and types of air within a home is not a simple matter. The 2015 MN Residential Energy Code is very specific in its requirements. It outlines not only the need for ventilation in homes but also addresses combustion air (air needed for fossil fuel appliances), make-up air (air that deals with sources of significant negative pressure) and provisions to protect homeowners from radon (a soil gas commonly found in MN that contains carcinogenic particles). Most homeowners are unfamiliar with building codes so finding a competent builder and HVAC contractor is highly recommended.
It’s good to see that most new single family homes in MN today are implementing HRV/ERV balanced ventilation systems to meet the total ventilation requirements of the MN Energy Code. Homeowners of older homes need not despair, for retrofitting an existing home with a balanced HRV/ERV ventilation system is not overly complicated or expensive.
If you’re in the process of building a home and want to keep it filled with fresh, healthy air year-round, then you have an important decision to make – which ventilation system to add to your HVAC package.
The most effective ventilation options available for residential homes are HRVs and ERVs. In order to choose the right one for your home, it’s important to understand the differences between the two products.
Both HRV’s (such as models produced by SummerAire Mfg) and ERV’s (like those produced by Solar & Palau – S&P) perform the same basic function in your home, essentially removing stale indoor air and replacing it with fresh outdoor air. Both products include exhaust and supply fans, along with a plate-type energy transfer cell/core that both the exhaust and supply air streams pass through. The outgoing air stream tempers the incoming air stream in a process referred to as an “energy transfer”.
In HRVs, the heat in the stale exhaust air is used to raise the temperature of the incoming outdoor air as it enters your home during the heating season. This process reduces the energy used by your home’s heating system to raise the outside air up to the temperature set point on your home’s thermostat. HRV cells are made out of non-permeable materials such as aluminum or a plastic composite which doesn’t allow any cross contamination of the exhaust or incoming air streams.
An ERV, also known as an enthalpy recovery ventilator, differs from an HRV because the material the cell is made out of is permeable (often a paper composite), allowing some of the moisture in the exhaust air to transfer into the incoming outdoor air which is often moisture deprived during the heating season in cold climates.
In more technical terms, the more humid indoor air equalizes the humidity of the drier air in order to make the humidity level in a home more comfortable and healthy (the HVAC industry recommends maintaining humidity levels in living spaces between 35-45%. In the cooling season, the ERV will reverse the transfer to remove humidity from the incoming fresh air before it enters a home. This saves energy by reducing the load on your air conditioning system and/or dehumidifier.
Both HRVs and ERVs help reduce the stress on your HVAC system compared to other ventilation methods. Both options are sound, and the decision really comes down to your climate, lifestyle, and home design. A general rule of thumb is an HRV is more effective in cold climates and an ERV is better suited for hot humid climates that require considerably more cooling than heating.
Since outdoor air during the heating season is most often considerably drier than a home’s indoor air, running an HRV can significantly reduce humidity levels, thus requiring a humidifier to maintain the 35-35% humidity in a home.
On the other hand, cold temperatures are a concern with ERV’s because the moisture in the cell will freeze at what is referred to as the dew point (frost point) which can occur in many cold climates – the colder the winter design temperature is for a specific area, the more likely an ERV cell will be exposed to freeze up; a condition where ice forms within the cell and air flow is either reduced or completely inhibited from passing through the device. Most HRV’s have built-in defrost systems which keep their cells from freezing up while functioning cold climates.
No matter which system you choose, installing one or the other will help reduce energy consumption and costs while ventilating your home. Both types recommend a continually running fan, but the amount of energy saved is much greater than what it takes to keep the fan running. Energy efficiencies for both types can range from the mid-55’s to over 90%, though the most efficient units come at a much higher cost. However, when you factor the value of energy savings over the unit’s full life cycle, choosing the most efficient model can often make it a financially and ecologically sound investment.
In the end, there is not one right choice. The choice between a Summeraire HRV and S&P ERV is not as important as the decision to incorporate mechanical ventilation into your home. The leaky houses of the past simply cannot compare with the airtight house designs of today.
Current homes entrap airborne contaminants like bacteria, allergens, viruses, mold spores and toxins (such as formaldehyde gasses from glues used in many household materials). HRV or ERV ventilation systems help to reduce the concentrations of these contaminants in an effective and efficient manner. Since your family’s health is likely at the top of your priority list, don’t overlook the important role that proper ventilation in your home can play.
Homeowners are increasingly relying on VRF heat pumps and ductless mini-splits to keep their families warm during the heating season. At the same time, commercial property managers are relying more and more on these devices as well, thanks to the ease of installation, simple controls and unparalleled flexibility that they offer.
VRF and ductless mini-splits represent some of the most efficient kinds of heaters on the market. Whereas propane and oil heating systems rely on expensive fuels to operate, these heat pumps produce indoor warmth in a cost-effective, environmentally friendly way.
However, heat pump mini-splits can be overtasked when dealing with subzero temperatures. These conditions cause HP’s to eliminate the efficiency that makes them so desirable and to produce less heat affecting the comfort of the living space.
Installing an electric duct heater for supplemental heating is one of the best ways to address this dilemma. The result is a far more efficiency in terms of the overall system’s Heating Seasonal Performance Factor (HSPF).
There are several ways to mount and install your electric duct heater in a mini-split system. One of the most popular methods is to install the electric duct heater on the discharge duct of the air handling unit, effectively keeping the duct heater unit out of sight.
By choosing a device correctly sized to fit inside the discharge duct and handle the needed additional BTU load, supplemental heating is available when it is needed and not used when the outside temperature isn’t cold enough to need it. In order to maximize efficiency, you’ll need to choose an electric duct heater that offers modulation, such as Thermolec electric duct heaters.
Modulation allows the duct heater to rapidly switch on and off in response to the difference in temperature inside and outside the building it is installed in. Using a duct temperature sensor and an SCR control, the supplemental heater can provide just the right amount of thermal energy to satisfy the need for additional heat.
On extremely cold days, the heat pump outdoor unit shuts off while the indoor air handling unit continues to run. The air handling unit provides the air flow and the electric duct heater provides the right amount of BTUs needed to satisfy the heating requirements.
Heat pump systems are growing in popularity in today’s marketplace because of their impressive performance/efficiency ratings. With many brands and types toting efficiencies of 400+ %, the energy savings is difficult to ignore. Unlike the original heat pumps of years’ past (introduced in the 1970’s), today’s heat pump technology produces BTU outputs capable of providing full heating comfort for residential and commercial structures located in environments with outdoor design temperatures down to zero degrees Fahrenheit. Incorporate supplemental heat, such as a Thermolec modulating electric duct heaters, and the result is a heat pump system with no outside cold temperature restrictions.
Electric duct heaters are a convenient, affordable and effective way to provide heat to a room or ventilation duct system. Professional HVAC contractors have used these devices in residential, commercial and industrial HVAC systems for many years.
The main idea behind heating with an electric duct heater is adding heat to the air inside the duct in an efficient manner. Electric duct heaters can be used in a broad range of applications, some of the most popular of which are:
When choosing an electric duct heater for your home or workplace, you’ll want to keep the specific application in mind when deciding the model you need.
Electric Duct Heaters typically use one of two types of heating elements:
Electric duct heaters are either designed to be staged on/off or modulating. Of these two, modulation is the best way to control duct temperatures.
On/off design is typically chosen when a duct heater is controlled by a wall thermostat and used to maintain temperature in a room. Modulation is best when a heater is used to maintain a set temperature in the duct and is controlled by a duct thermostat. Modulating control uses just the right amount of heat to maintain the temperature set by the duct thermostat, saving energy and improving comfort.
Duct thermostats can control temperatures using electric, electronic and pneumatic controllers. Large systems may even benefit from a sophisticated Direct Digital Control (DDC) system. Electric duct heaters are designed to interface with any of these options and are available in virtually any size, power handling and voltage.
Both open-coil and tubular heating elements require air flow to transfer the heat from the elements to the air in the duct. If the air flow stops for any reason, temperature in the duct can rise to dangerous levels.
This is the reason companies like Thermolec install automatic thermal cut-off features as well as manual resetting thermal cut-offs. Air flow can be stifled by obstacles and debris without warning, making redundant safety features like these critically important.
For a standard HVAC system, selecting a heater is straightforward once the basics of electric duct heater operation are understood. It comes down to three steps:
With this information in hand, you’ll be ready to choose between the various affordable, high-performance electric duct heaters on the market.
When it comes to residential and light commercial heating, ventilation and air conditioning, a fast-growing market segment is quickly developing into an industry-leading trend. Ductless air conditioners, also called mini-splits, are increasingly replacing the large, bulky window-mounted systems of yesteryear. Is this a passing fad, or are there real benefits to be enjoyed by installing one of these systems in your home or workplace? Read on to find out.
The main difference between these new systems and traditional window air conditioners is that they are smaller, more efficient and more flexible when it comes to mounting and placement. Mini-splits allow homeowners to selectively heat and cool individual rooms according to their occupants’ desires by connecting a single outdoor unit to multiple indoor air controllers.
If you’re considering installing a mini-split air conditioner, you can expect to enjoy the following advantages:
• Increased Efficiency—According to , up to 30 percent of air conditioning energy loss is due to air seeping through imperfect ductwork. This ductless air conditioners bypass ducts entirely, there is no subsequent energy loss, making these devices robust energy savers.
• Easy Installation—Although ductless mini-split systems may seem complex to install, they are actually simpler than most packaged air conditioner systems. For example, installing the EMI Iverter by ECR International requires only a single three-inch hole be drilled into the wall. Since air conduits can be easily extended, the outdoor unit can be mounted anywhere for convenience.
Ductless air conditioners come with remote controls so that tenants and guests can adjust air flow and temperature without having to physically access the device. This means that both the indoor and outdoor units can be effectively hidden from view, which is very valuable and comfortable from a design perspective.
Although this technology offers sufficient benefits to merit investment on any homeowner’s behalf, the units themselves can be more expensive than window units or evaporative coolers. In structures that don’t already have extensive ductwork installed, however, they are a much cheaper and more reliable option than installing a central air unit.
This price difference can be covered through energy savings over the estimated 12-15 years of an air conditioner’s service life, however, since even the best ductwork still produces energy loss. In some conditions, the fact that the outdoor unit produces water through condensation can be troublesome, but proper installation and placement takes care of that issue conveniently.
For more information on comparing mini-split ductless air conditioners with central air units, window units and evaporators, consult this useful infographic made by Energy.gov.
If you have a high-powered, commercial-quality cooktop installed in your kitchen, chances are you also have a makeup air unit installed in your home. This device compensates for the amount of air being pushed out of your kitchen’s extractor and breathes fresh, room-temperature air in from outside. Makeup air units are typically automatic—unless you had yours recently installed, you may not even know you have one, but you’ll notice if it breaks down.
If your cooktop comes with a large extractor hood that sweeps out odors and contaminants from your home, your makeup air system is what’s responsible for replacing the lost air. Without it, your home would be depressurized and the kitchen hood would soon be unable to push the air out. The fumes would collect inside your house—creating a dangerous environment for you and your family.
Fortunately, makeup air units are built to last, and if you take care to have yours regularly inspected you can catch any problematic developments before they seriously affect the device’s ability to function safely. Robert Tinsley of HPAC Engineering suggests biannual inspections for the best results. Have a certified HVAC technician examine the following:
The filters, fan wheels, burners and orifices of the device generally only need to be cleaned. They will work perfectly as long as they are not covered or clogged with debris.
It can be helpful to think of your makeup air unit as just one part of an overall kitchen ventilation system. If the unit is working perfectly but the kitchen extractor hood is filled with gunk and debris, it stands to reason that you’ll experience some unexpected results.
Cooking hoods are simple to clean, requiring no more than elbow grease and a good cleaning solvent. Most contain some kind of filter that requires regular replacement—make sure that it isn’t obstructed, and consult Cleanipedia’s guide for more specifics on keeping it grease-free. With both these appliances in good shape, your home’s interior air pressure should remain in perfect equilibrium.
It’s no secret that U.S. homeowners are becoming increasingly attracted to the idea of installing high-powered, commercial-quality kitchen equipment in their homes. The widespread availability and increasing affordability of these devices makes them a common sight in American kitchens.
At the same time, residential building contractors are designing homes that are more airtight than ever before. As a result, house depressurization and its associated risks are on the rise, making reliable makeup air solutions a necessity for many households.
House depressurization occurs when the air pressure inside the house is lower than that of the atmosphere outside. This creates a system of negative pressure. According to the EPA, this can cause exhaust gases, such as those produced by combustion-based kitchen appliances, to backdraft into the home. This accumulation is dangerous for residents and can promote the growth of mold, placing the integrity of the structure itself in peril.
In order to create an indoor pressure system that pushes exhaust gases out, home contractors typically install either engineered openings or mechanical ventilators. However, this approach does not provide adequate air infiltration for larger kitchen ranges.
According to the Pennsylvania Housing Research Center, exhaust hood systems capable of exhausting in excess of 400 cubic feet-per-minute (CFM) require the installation of a complementary makeup air system. The system must be automatically controlled to start and operate simultaneously with the exhaust system, in accordance with International Residential Code M1503.4.
Since the unit needs to both push air inside the home and heat the air to a temperature that does not negatively impact the home, an appropriately powered unit is necessary.
Although simply choosing a makeup air unit with the same CFM-rating as the kitchen exhaust seems like a logical idea, actually choosing the right unit is a little more complex than that. This is mostly due to the difference in temperature the unit has to compensate for. In order to determine how powerful a makeup ventilation system is needed for a particular kitchen appliance, we need a few figures:
High-powered commercial cooking ranges generally include information about their exhaust rates, given in CFM. If that information is not immediately available from the appliance manufacturer, it may be necessary to arrive at an estimate based on the type and power consumption of the unit. The American Society of Heating, Refrigerating and Air Conditioning Engineers sells a handbook that contains the information needed to make this estimate.
Arrive at the desired temperature rise by subtracting the coldest likely design temperature from the home’s desired room temperature. This number will be multiplied by the CFM of the appliance and then divided by the number of BTUs-per kilowatt the makeup air system uses, arriving at the desired kilowatt performance of the heater.
HVAC manufacturers like Thermolec typically include BTU-per-kilowatt figures in their product specification sheets. So if a homeowner needs to displace 400 CFM even when the outside temperature is 20°F and the ambient room temperature is 70°F, using a Thermolec Makeup Air Model FER-8-6-240, the equation would look like this:
(70-20) x 400 ÷ 3.412 = 5.86 Kw
How do we know that this is the appropriate figure for that particular model? Going back to the specification sheet, we can see that the FER-8-6-240/1 has an 8-inch collar size and delivers a maximum of 6 Kw—meaning that it’s the correct model for this example even though it has a reported CFM of 300.
This is typical of the Upper Midwest, where state regulations explicitly require units be powerful enough to compensate for large differences in temperature. As a result, people who live in colder climates will need to adjust accordingly by calculating the actual CFM using the above equation.
Heating your home with a heat pump is energy efficient and cost-effective. When dry indoor air becomes a problem in winter, however, you’re likely to find that the central humidifiers that work just fine with fossil-fuel-fired furnaces aren’t as effective when used in conjunction with a heat pump. Fortunately, a steam humidifier may be the solution to the problem.
At best, dry indoor air is a nuisance. It can make your skin itchy, your lips dry and cracked, and your throat irritated. It can even make your nose bleed.
For some, those minor irritations can lead to even more serious problems. When dry air irritates your throat and your nasal passages, you’re more susceptible to respiratory illnesses such as cold and flu, sinus infections, and reactions to allergens. Asthma sufferers may experience more frequent or more severe asthma attacks when the air is dry, too.
Dry air isn’t kind to your home and the things in it, either. Low humidity can cause wood floors and finishes to dry out, shrink, and crack; wood furniture is vulnerable to damage caused by dry air, as well.
Perhaps worst of all, we’ve all experienced the inconvenient—and sometimes painful—build up of static electricity that occurs when dry air helps surfaces hold their static charges.
Many home heating systems incorporate a humidifier that works by bypassing some of the warm air generated by the furnace through an evaporator pad that’s saturated with water. As the warm air flows across the pad, it picks up some of the moisture from the pad, and that moisture is distributed through the home’s heating ducts. Over time, the added moisture increases the relative humidity of the air throughout the home.
Steam humidifiers, such as those manufactured by Thermolec, take an active approach to raising your home’s humidity. In these systems, a sensor called a humidistat recognizes when the air in your home is too dry, and when the humidity drops below a specified level, the humidistat triggers the production of high-temperature steam in a reservoir attached to the system. That steam is then mixed with the heating system’s warm air and is sent throughout the house, raising the humidity of the indoor air.
Steam humidifiers use less water than bypass humidifiers. Bypass humidifiers often use as much as 15 gallons of water to produce one gallon of water vapor, while steam humidifiers can produce almost one gallon of vapor for every gallon of water used.
Steam humidifiers also typically require less maintenance than bypass humidifiers, whose evaporator pads need to be replaced at least once a year. Thermolec’s Acu-Steam system is designed to operate for more than 10 years without needing a replacement canister or heating element.
Steam humidifiers are especially advantageous in homes heated by heat pumps. Heat pumps typically produce warm air with a lower temperature than that produced by gas- or oil-fueled furnaces, and bypass humidifiers don’t work as well when the air passing over the evaporator pad isn’t warm enough.
Steam humidifiers generate steam using their own heat source, so they don’t rely on the temperature of the heating system’s air to produce moisture. As a result, they’re able to consistently introduce more moisture throughout your home when working in conjunction with the relatively low-temperature air put out by the heat pump.
Working in coordination with one another, a heat pump and a steam humidifier prevent dry winter indoor air from making your home uncomfortable and unhealthy, and they do it in the most energy-efficient, cost-effective, hassle-free way possible.
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