Modular homes can be more energy efficient than on-site built homes if designed with that intention in mind. A home is energy efficient when it reduces the energy consumption and demands, becoming more cost-effective and sustainable. While any modular home could be built to be an energy efficient home, it requires a Smart Design to achieve Energy Efficiency.
The concept of smart design consists on the combination of passive and active strategies which we will deepen into by defining how are modular homes energy efficient and exploring each one of the different aspects that need to be considered to ensure a modular home is energy efficient:
- Location and orientation of the house
- Insulation and Windows
- Building Materials and Thermal Mass
- The importance of ventilation and Heat Recovery
- Heating and cooling Systems
- Energy Efficient appliances and Lighting
- Alternative energy solutions
Energy efficient modular homes are becoming more and more popular in the recent years since the climate change crisis is becoming more evident and people are growing into a more conscious mind-set. While they have unquestionable economic and environmental benefits, energy efficiency comes with some extra hidden benefits worth considering.
Smart Design to achieve Energy Efficiency
An energy efficient home is a house that uses less energy to perform the same task [1], reducing the amount of energy consumption (electricity, gas and even water) while offering comfortable living conditions inside. In order to build a house that offers all the basic needs while cutting down the usage of energy we require a smart design that will consider both Passive and Active strategies.
Passive design strategies
Passive strategies are design methods integrated in the construction thought to reduce as much as possible the need for artificial energy consumption (active design strategies). To properly apply these strategies we need to understand the climate where we are building and the needs that will be required indoors, since passive strategies utilize the natural elements on site [2].
For example, if our energy efficient modular home is placed in a very hot weather our passive strategies will consist on preventing the sun rays from entering inside the house unfiltered, especially through a window glass, to avoid a greenhouse effect that will overheat the indoor air and demand for an air conditioning system to lower the temperature to comfort standards. In a very cold climate however, we will do the exact opposite, and try to capture as much sun rays as possible to heat the place naturally and therefore reduce the need for heating systems.
We can employ a number of practices to create our smart passive design; the more strategies we incorporate the better our energy efficient modular home will perform in:
- Location and orientation of the house
- Insulation and Windows
- Building Materials and Thermal Mass
Active design strategies
Active strategies are those that use or produce energy such as electricity or natural gas. Some examples are air conditioning, heaters or light [2]. Any energy efficient home will try to reduce as much as possible the need for active strategies while choosing devices that are designed to save more energy such as those rated with the Energy Star [3].
Systems that generate energy such as solar panels or geothermal energy exchangers are also considered Active strategies. It is common for energy efficient homes to include some of these active design strategies in order to provide clean energy to supply the energy demands.
Some of the most important Active design strategies to consider in an energy efficient home are:
- The importance of ventilation and Heat Recovery
- Heating and cooling Systems
- Energy Efficient appliances and Lighting
- Alternative energy solutions
How are modular homes energy efficient?
Location and orientation of the house
Before we start designing an energy efficient modular home, we need to understand the climate as a means of where we are constructing. We can start designing the energy efficient passive strategies in the moment we identify the weather characteristics of the location and during the conceptual design phase. By understanding the location and orientating the home properly we are already utilizing some of the most important site natural elements.
A comfortable indoor temperature should remain between 20 to 26ºC (68 – 79ºF) [4]. If temperatures outdoors are very hot all year long, our modular home will need to be designed in a way that the sun doesn’t overheat the indoor air. In this situation a location that receives a heavy shade or a site with plenty of trees would be ideal. In terms of orientation, we will try to avoid orientating the main facades of the house towards those directions that receive the most sunlight. We will though, be careful about the amount of light received, we are trying to keep the heat outdoors to not require cooling active systems but we need to keep the natural lighting levels as bright as possible to reduce the amount of artificial lighting required. In case the climate is cold all year long the home should follow the opposite strategies, since it will require receiving as much sun as possible to naturally heat the indoor air. Therefore, the ideal building site will have unobstructed sun and be protected from the wind to maintain the temperature indoors as warm as possible. When deciding the orientation of the main facades of the building we will choose those directions receiving the most amount of sun.
Those climates where temperatures can both drop low and rise high depending on the season, will in general look for a location that receive a good amount of sun and orientate the main facades towards the sunlight. Yet, they will use design strategies integrated and built into the house such as canopies, pergolas or shutters; to protect from the sun rays and heat when the temperature rises.
Insulation and Windows
Insulation is a very important element required in an energy efficient home and all modular homes built today are well insulated, even those that are not classified as energy efficient, since they are still built up to building code standards [5] and therefore they will be as warm in winter as an on-site built house. However, those modular homes that aren’t only designed to function well but that aspire to operate as energy efficient constructions require special attention to the insulation materials and process.
While all modular homes will be properly insulated, efficient homes offer an extra care to the insulation and air tightness of the building to reduce the amount of heating required. Areas like the joint between the wall and the window are locations that need to be carefully designed to avoid air leaks since they will lead to heat loss. Choosing windows with the Energy Start certificate or NFRC labels can be a good start to ensure a good energy performance [6]. Some modular home companies such as Dvele Homes, design their houses to match Passive house standards [7] and take very good care of the building insulation and air tightness to avoid heat loss, managing to use a 65% to 75% less energy than a standard home [8].
Building Materials and Thermal Mass
While deciding to build with sustainable materials is always a good idea, for a modular home to be classified as energy efficient materials are not required to be environmentally friendly. However, there are some other aspects that are interesting to consider when going for an energy efficient home such as choosing materials with a high thermal mass which is the ability of a material to absorb, store and release heat [2]. Concrete for example, is a great example of a material with high thermal mass. During the day, when hit by the sun rays, concrete will absorb the temperature, heating up and storing it within itself. At night as the temperatures drops, the concrete wall will release and disperse this heat in the area around it. Thermal mass is as good as thermal insulation and in some weathers they are exchangeable even though it works in a different way. However, as insulation, thermal mass when utilized properly allows the building to regulate its indoor temperature naturally reducing the requirements for heating and cooling systems.
The importance of ventilation and Heat Recovery
Mechanical ventilation is a key element in energy efficient modular homes. As we have seen when discussing isolation, air tightness is necessary to avoid heat loss and maintain a good indoor temperature naturally. However, circulation of supplying and extracting the air indoors is necessary to maintain the necessary levels of Oxygen, eliminating the excess of Carbon Dioxide and overall keeping a clean and healthy indoor air.
Energy efficient homes integrate a mechanic ventilation system with heat recovery to provide fresh air all year round [9]. The temperature indoors will be highly different from the outdoor temperature and it is easy to lose or gain heat with the ventilation system. To avoid this issue, a heat recovery system will be installed avoiding temperature loses and reducing the energy consumption of air conditioner and heater [10].
Heating and cooling systems
All the strategies discussed previously are designed to avoid or reduce the need of heating and cooling systems. However, most energy efficient modular homes will still require some help maintaining a comfort temperature indoors. There are many different systems for heating and cooling, in an energy efficient modular home we will choose those with a good energy performance such as those certified with the Energy Star. To ensure a modular home is energy efficient and the heating and cooling systems utilized have a good energy performance, it is recommended to opt for a modular home company that has experience in the area and understands well how to design a home with these requirements. Method Homes for example, built its homes up to Net-Zero requirements and uses high efficiency heating and cooling systems that are 250% to 300% more efficient that the standard ones, to choose from a ductless mini split or hydronic radiant heat [11].
Energy efficient appliances and Lighting
While an energy efficient home will be smartly designed to receive as much daylight as possible in order to reduce the artificial lighting required indoors, every energy efficient modular home in our modern society will still need to provide artificial lighting and appliances. Since both lighting and appliances can consume a great amount of electricity, those need to be checked very carefully before being installed in an energy efficient home.
The most popular choice for energy efficient lighting is the use of LED light bulbs. Those use about half the amount of energy than what other light bulbs use, have a longer life-spam and are easily paired with dimmers, which increases their capability to save even more energy [12].
When choosing appliances for an energy efficient modular home we must select those with high efficiency that meet the regulated targets for energy consumption. If your modular home company is ensuring you an energy efficient house and it includes the appliances packages in the final product, they will take into consideration the energy consumption of those appliances. However, if the appliances are not included in the package, you should be very careful with your choices since the amount of energy consumed by each appliance can vary enormously. Every appliance will come with labels indicating how efficient it is, the more stars, the more energy efficient it will be [13]. If you live in the United States, choosing an Energy Star certified appliance will guarantee the high energy efficiency standards for most household appliances [2].
Alternative energy solutions
A more sustainable energy solution to fulfil the energy demands is always a great idea to provide clean and “free” energy for your own usage. By producing its own clean energy, the energy efficient home can become a Net-Zero home meaning “it will make as much energy on-site as it will consume over the course of one year” [14]. This will result into having a cost zero on the electric bill since the few amount of energy that the house demands to achieve comfort is produced on-site and powered by natural means. Some modular home companies are already setting themselves ahead and offering these smartly designed homes, such as Plant Prefab for example, who designs every one of their homes to meet Net-Zero standards [15].
The most common source of residential renewable energy in the United States is Solar Power, even though there are other possible energy options such as wind energy, micro hydro power and hybrid systems which combine solar and wind powers [16]. Most of the modular home companies offering energy efficient homes offer photovoltaic solar installation or offer the option of leaving it all prepared for its future installation once the house is assembled on-site. Installing Solar panels has an extra cost to pay up front during construction but it usually pays back in the long run at around 8 years [17].
While modular homes aren’t energy efficient by definition, there is a great selection of modular home companies that offer the opportunity to build up to energy efficiency standards. Choosing an energy efficient modular home might increase the cost of construction but it will definitely reduce the utilities bill cost enormously afterwards. However, the energy cost isn’t the only benefit of an energy efficient modular home:
- Lower utility bills: As we have mentioned one of the biggest benefits of energy efficient homes is lower utility bills cost. The reduction or even avoidance of heating and cooling systems, together with a smart choice of highly efficient lighting and appliances lead to big reductions in energy use (electricity, gas and even water) [18].
Moreover, if we choose to include alternative energy sources to provide our own demands, the electricity bill is highly reduced and can even be 0 with a Net-Zero energy efficient home.
- Environmentally friendly: A lower environmental impact is one of the big benefits of energy efficient modular homer. Since the energy demands are highly reduced, the gas emissions and greenhouse effect are significantly lower than those emitted by a standard house.
- Improve comfort: The perfectly isolated walls and thermal mass materials, the complete air tightness around the building envelope, and the highly controlled ventilation system with an integrated heat recovery unit; ensures a comfortable environment indoors, maintaining a warm and stable temperature in winter and a cool feeling in summer.
- Healthier environment: The air quality indoors improves drastically in an energy efficient modular home since the usage of air conditioning and heating devices is highly reduced. Moreover, the heating and cooling systems chosen for its efficiency properties are in general healthier choices that have a lessen influence on the indoor air quality and that include filters which will avoid the entrance of air particles such as pollen or pollutants. The mechanized ventilation system also contributes to a healthier environment since it ensures a constant air renovation and maintains balanced levels of Oxygen, Humidity and Carbon Dioxide.
Modular homes can get to an energy efficient standard by applying and balancing what passive and active strategies can offer into the design of the home. Knowing the specifications on how modular homes are further constructed on the bases of energy efficiency can show a great outcome for all present and future home owners.
References
- Energy Efficiency EESI,Environmental and Energy Study Institute https://www.eesi.org/topics/energy-efficiency/description
- Passive Design and Active Building Strategies Sustainable https://www.sustainable.to/strategies
- About Energy Star, Energy Star® https://www.energystar.gov/about?s=mega
- Indoor Temperature: Staying in the comfort zone Roockwool International A/S https://www.rockwool.com/group/about-us/our-thinking/indoor-comfort-health-and-safety/indoor-climate/indoor-temperature/
- How well insulated are modular and manufactured homes? Preferred Homes https://preferredhomesmi.com/uncategorized/how-well-insulated-are-modular-and-manufactured-homes/
- Update or Replace Windows Energy Saver, U.S. Department of Energy’s (DOE) consumer resource on saving energy and using renewable energy technologies at home. https://www.energy.gov/energysaver/update-or-replace-windows
- About Passive House – What is a Passive House? Passive House Institutehttps://passivehouse.com/02_informations/01_whatisapassivehouse/01_whatisapassivehouse.htm
- Frequently Asked Questions – Are Dvele Homes Sustainable? Dvele© https://www.dvele.com/frequently-asked-questions
- Ventilation & Heat Energy Recovery Passivhaus building performance in Australia by PASSIVE HOUSE Pty Ltd http://passivehouse.com.au/page/ventilation—heat-energy-recovery
- What is a Heat Recovery Unit? Casals Ventilación Air Industrial, SLU https://www.casals.com/en/ventilation-tools/concepts/what-is-a-heat-recovery-unit/
- Sustainability . Responsible Design + Construction Method Homes® https://www.methodhomes.net/sustainable-design
- 23 key features of an Energy Efficient Building Aeroseal Headquarters https://aeroseal.com/air-duct-sealing-blog/energy-efficient-building-design/
- 15 Tips for Designing Energy Efficient Building ArchiStar Academy https://academy.archistar.ai/15-tips-for-designing-energy-efficient-buildings
- Fixsen A. (July 7, 2020) How to design a Net-Zero Home Architectural Digest Magazine https://www.architecturaldigest.com/story/how-to-design-a-net-zero-home
- Frequently Asked Questions – Sustainability. Does Plant do LEED certification, net zero or passive homes? Plant Prefab, Inc. https://www.plantprefab.com/faq
- Green, D. (March 31, 2021) 14 Energy-Efficient Home Features to look for when House Hunting Homebuyer https://homebuyer.com/learn/energy-efficient-homes
- Aggarwal, V. (January 13, 2021) How to calculate solar panel payback period (ROI) Energysage https://news.energysage.com/understanding-your-solar-panel-payback-period/
- Top 7 Benefits of Energy Efficient Homes Morningston Estates https://morningtonestates.com/blog/energy-efficient-homes-benefits/
