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Heat Recovery System Design
Commercial buildings located in areas where cold weather is continuously present may need additional infrastructure support to maintain interior temperatures. there are a variety of ways to do this. One way is to design a heat recovery system that will help maintain the interior temperature of the structure. This heat recovery system will support the existing heating equipment not replace it. An MEP engineer will be able to review your existing building or plans and help you determine the type of heat recovery system you will need to achieve your project goals. knowing these goals ahead of time will streamline the heat recovery system design process.
In places like Chicago where the outside temperature can be drastically low, this means that the interior air in structures will also be drastically low. adding a heat recovery system chewy structure to support the main heating system will increase energy efficiency and add to the life of the main heating system. it may also lower maintenance costs on the main heating system.
In large commercial applications especially where a high occupancy rate is present, a heat recovery system can book a number of different ways. there are traditional heat recovery systems and there are a few out of the box options that may be better for your specific application. A local MEP engineer will know a few of these options and may have experienced designing for your specific industry. It is highly recommended that you seek out an MEP engineer that is familiar with your building needs and the local weather.
What are the goals of a heat recovery system?
A heat recovery system is considered to be one of the best ways to maintain Energy Efficiency without sacrificing interior temperatures. they are designed to deliver rewarmed outdoor air into the space. This creates an environment that is easier for the main heating system to heat the inside air. Because the main heating system is reliant on the temperature of the air within the structure, extremely cold air in the structure can make it difficult for the heating system to complete its run function. Replacing extremely cold air with pre-warmed air shortens the time the heater needs to run in order to raise the temperature in the space.
Not only do heat recovery systems help reduce the run time of the main heating system, they can also help lower the amount of condensation and moisture in the interior air of a structure. This is especially important in places where moisture causes mold, mildew, and bad air quality for occupants. Including a Heat recovery system in your building design, will ensure the end users are able to enjoy the structure mostly moisture free. Being able to remove the moisture in the air offers a better occupant experience. it also prevents physical asset damage to things like furniture, electronics, and other high-end fixtures in the structure.
Historically structures were built in such a way that naturally occurring pollutants etc, were able to be released through gaps and cracks in the structure. With the advent of designing and building “tight” structures for energy efficiency etc, those natural pollutants are no longer able to escape the structure. Therefore, another goal of the heat recovery system is to ensure these natural pollutants are able to leave the structure and not build up over time. Examples of these pollutants are pet dander, mold spores, dust mites, allergens, tobacco smoke, and other pollutants. All of these elements can lead to poor air quality in your building. Designing and installing a well thought out heat recovery system can help these pollutants be expelled from your building. Thus, improving air quality and the occupant’s building use experience.
The goals of a heat recovery system ultimately will be dependent on the end use of the building and what the occupants of the building will need. Be sure to take those factors into account when you are designing the heat recovery system. Outlining these goals before you begin designing, will ensure that the heat recovery system design is an accurate reflection of what is needed.
How do you size a heat recovery system?
There are a few components to consider when designing a heat recovery system. One of them is the size of the heat recovery system. determining the size of the heat recovery system you need for your building application before you begin building is imperative to project success. While there are some practical things you can do to determine the size of a heat recovery system for your building, it doesn't replace the expertise of an MEP engineer. Before plans are submitted 4 building approval, be sure to consult an MEP engineer to ensure you have selected the best equipment and determined to the correct size for your heat recovery system.
Determining the size of your heat recovery system is dependent on a number of factors. these include building usage, occupancy rate, airflow, square footage of the building, room count and environmental factors. some of these factors you will be able to determine and verify yourself. while some of them will need an expert to weigh in. Be sure to consult with that expert before you make your final selection. your heat recovery system could impact the structure of the other mechanical systems in your building. Additionally, the other mechanical systems and plumbing Systems in your building could become part of the heat recovery system. This will have an impact on any calculations that may have been done previously to size and design your system.
Calculating the required air flow in your structure is just one of the factors you will need to consider when sizing and designer your heat recovery system. For a traditional heat recovery system, where you replace interior air with pre-warmed air, it is a simple set of calculations. The 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 building. The simple equation goes like this in a residential application:
Occupants x 7.5 + square feet of conditioned floor area x 0.1 = ventilation rate in cfm
So, four people living in a 2,000 square foot home would need a continuous airflow of
(4 x 7.5) + (2000 x 0.01) = 50 cfm
For commercial applications, you will need to consult with an MEP engineer to determine the required air flow for your building application.
As with every mechanical system design, ensuring you have the proper equipment is paramount to project success and the owner’s stamp of approval. Sourcing the proper equipment for large commercial applications will require engineers and industry experts. Selecting the right equipment should not be taken lightly.
Steps to take to begin designing your heat recovery system
Review Heat Recovery Systems vs Energy Recovery Systems
There are two types of energy-recovery systems: heat-recovery ventilators (HRV) and energy-recovery (or enthalpy-recovery) ventilators (ERV). Both types of ventilators include a heat exchanger core, one or multiple fans to push air through the mechanical equipment, and some other controls. The most obvious difference between a heat-recovery ventilator and an energy-recovery ventilator is the way the heat exchanger core works. In an energy-recovery ventilator, the heat exchanger transfers a certain amount of water vapor in addition to heat energy. A heat-recovery ventilator only transfers heat and not water vapor.
The part of the country in which you are building the structure will dictate what type of unit that is right for your needs. Generally speaking, HRVs are usually recommended for colder climates that have longer heating seasons. Alternatively, ERVs are used for warmer, more humid climates with long cooling seasons.
Take the Time to Locate Exhaust Points
Since the idea is to remove humid, old air from the commercial structure, locate the stale air exhaust points in each bathroom, kitchen, utility room, and other high moisture areas in the commercial structure. If you are working with new construction and are still in the design phase, use your detailed plans to locate all exhaust points. This allows heat recovery from areas of the building where humidity and odors are most abundant. The heat recovery system can replace spot ventilation (exhaust) fans in some of these rooms to save money and provide a more pleasant environment. Any room that has a function where humidity would be created by occupant activities, a heat recovery system will be helpful. An exhaust point that is located near the kitchen area should be at least six feet from the cooking surface. This exhaust point is intended to remove general moisture in the air and cooking odors.
Be Sure to Locate Fresh Air Supply Points
In order to mix fresh air throughout the building, supply points should be positioned a considerable distance from the exhaust points. Bedrooms and living rooms are good choices. Although the incoming fresh air has been tempered and warmed by the heat exchanger, it’s usually slightly below socially normal room temperature. Taking into account where the occupants will be sitting or occupying the space will help avoid having the air blow directly onto them. It is recommended to place the incoming vents high on a wall, so it will mix with warm air and not be noticed by the occupants.
Creating a Dedicated Duct System is Recommended
Most experts agree that it’s best for an HRV to have its own dedicated duct system. If the building has hydronic heat or ductless heat pumps, that’s the only choice. In this case, the HRV mixes the air throughout the building. However, buildings with forced air heating and cooling systems can use those ducts. This saves money on material and labor and offers great distribution of fresh air. Integrating HRVs with forced air systems requires careful planning, review from an MEP engineer, proper controls, and sound installation practices.
How can an MEP engineer help you design your heat recovery system?
A qualified MEP engineer can help you design your system based on a number of factors. The engineer is required to have a certain level of construction and mechanical, electrical, Plumbing knowledge. They are also required to know and understand the load calculations necessary to size MEP equipment. Their experience and knowledge gives them the basis to effectively and efficiently size your MEP equipment.
A local qualified MEP engineer will have knowledge and understanding of the local building codes and local governing bodies for the commercial construction industry. They are your expert boots on the ground in the mechanical, electrical, plumbing areas of your project. The MEP engineer is a vital component of your construction team and someone who you should use as a reliable resource. If your general contractor does not have an MEP engineer in-house, do your due diligence and find one that you work well with.
The MEP engineer will be able to review the plans you have drafted with your architect and with all of the information you have gathered on the size of equipment you think you need, they will be able to determine your next steps and the direction you need to go. They may need to conduct additional or complementary research and inquiries to verify they are making the correct recommendation for the design for your application.
Calling on the experts like an MEP engineer will help your project succeed in the long run and help you to continue being profitable and efficient. Knowing when to call in an expert is a valuable skill to have. If you think you need an MEP engineer please take a moment to contact us and we would be happy to review your project information. We are pleased to serve the Chicago area and welcome local and out of state clients.