Unless you buy an off-the-rack prefabricated eco-friendly home without modifications, you’ll probably need to do some serious thinking about the design of your home to make it truly eco-friendly. And, even if you do go with a specific model sold by a prefab home company, chances are there’ll be optional upgrades to consider and decisions to make based on the size, location, and orientation of your lot.
Getting to design your very own eco-home is no small undertaking, and it’s easy to get wrapped up in small details and lose sight of the bigger picture. That said, sweating the small stuff really matters in a prefabricated tiny home.
In this quick guide, I’ll go over some of the key considerations for designing an eco-friendly prefabricated home. Let’s start with some basic tips that can save you time and money and keep construction waste to a minimum.
Build your non-standard home using standard measurements
If you’re designing a home from scratch, get to know the standard industry sizes for materials (timber, insulation, piping). This can maximize cost efficiency in your prefabricated home-build because you can get pre-cut timber that was digitally cut at the factory, meaning it’s more likely to be cut accurately compared to timbers cut on site.
In practice, this means having a blueprint that uses 4-and 8-foot increments rather than, say, 5- or 9-foot timbers. Taking this approach also helps you to minimize waste and keep costs low. And it makes it easier to find replacement materials quickly and cheaply should anything go missing or get damaged. Some prefabricated home companies charge you only for materials used, not for waste materials (because they repurpose these in other projects).
Take a look at standard measurements for eco-friendly insulation materials too. This may affect where you position outlets, piping, and other things in your eco-home design.
Top Tip – For the elements of our home that aren’t prefabricated, check out local listing sites and groups, as well as Craigslist, etc., to see if your neighbors are giving away scrap building materials leftover from their own projects. You’ll be amazed at the things you can get for free, including timber that was surplus to requirements or cut incorrectly, insulation materials, piping, tiles, and other things that can cut your costs significantly. Make a habit of following these listings for a few weeks to see if you spot any patterns, then finesse your design with these free or low-cost materials in mind.
Match your design to your lot
If you’re looking to build a modular or prefabricated home on land you already own, consider doing a site inspection with a contractor and/or with a member of any prefab team you’re considering working with. This will help you to get a sense of the kind of designs that make sense for your specific lot.
The kind of things you want to factor into your design choice include:
- The slope of your lot – will a terraced, multistorey prefab design work best, or a single level design?
- Access – is there a steep driveway that will make it hard to bring in modular pieces?
- Sun exposure – can you take advantage of passive heating and cooling, and set up a solar array?
- Drainage – will you have problems with rain, snow, and groundwater if you choose an earth-sheltered or below grade design?
- Wind – do you need to double down on insulation; will your wind turbine actually generate power?
- Radon – does part of your lot have higher or lower levels of this radioactive gas? Get it tested!
An experienced contractor can let you know right away of a particular home design is going to prove difficult or impossible given the properties of your land. A prefab company can also give good advice about the suitability of their standard designs for your lot, and offer possible modifications that will save you money and give you a more energy efficient and comfortable home. Beware any prefab company that just wants to sell you a home without considering where the home will be situated. The best companies want you to love every aspect of your prefabricated home and will suggest modifications to make sure this happens.
Energy-efficient house shapes
Oddly enough, many prefabricated off-grid tiny homes aren’t designed with a particularly efficient shape in terms of energy and material use. Unless you have very specific space constraints, such as a narrow trailer on which to place and transport your home, it pays to think outside of the box when designing the shape of your eco-home.
Many tiny homes are narrow and tall, while other prefabricated and modular homes are long and narrow. Neither is ideal for material and energy use as they have a poor ratio of living space to exterior walls.
Consider, for example, that in most U.S. states a home intended to fit on a trailer can be a maximum of 13.5 feet tall, 8.5 feet wide, and 40 feet long. Most tiny homes are actually smaller than this, at less than 400 square feet of living space. For simplicity’s sake, imagine a tiny home measuring 8 feet by 40 feet, offering 320 square feet of space on the main level and 80 square feet of space on a mezzanine level. This home would have 96 feet of exterior wall, plus that big sloping cathedral roof (where it’s hard to stuff insulation).
In comparison, a home offering the same amount of living space (400 square feet) but measuring 20 feet by 20 feet would have just 80 feet of exterior wall. This translates to less timber, drywall, insulation, and other materials, lower labor costs, and significantly less energy spent heating and cooling the home. Tiny homes and prefabs with narrow, long shapes can also make it tricky to find energy efficient appliances that fit the space, and may affect your choice of insulation materials.
Indeed, many tiny homes use spray foam or XPS foam board insulation because this seems like the only way to approach being somewhat energy efficient when space is at a premium. Surprisingly, even some supposedly eco-friendly prefabricated homes also use foam insulation, which is notoriously bad for the environment, being made with petrochemicals and emitting vast amounts of greenhouse gases. And, if you use spray foam to insulation your home (which is common for fiddly tiny homes), all the off-gassing happens on site, with a serious impact on the indoor air quality of your small, air-tight home. Yes, insulating your home well will help reduce the amount of energy you need to heat and cool it, but at what cost to the environment and your health?
If you want to avoid using industry standard toxic insulation foam, you have two options: consider alternative designs that reduce how much insulation you might need; and look for more eco-friendly insulation materials. If you choose the latter option, think about how each material responds to moisture, whether it will meet fire safety regulations, the potential hazards of working with the material in the factory or on-site, and how effective the material is at different thicknesses (this can be a big deal in a narrow tiny home). You’ll probably want to read up on R-values for insulation as different companies use different measures, which can get rather confusing.
Future-proof your home design
If you plan on living a somewhat nomadic lifestyle in your new tiny home or prefabricated modular home, it’s a good idea to account for that right from the start rather than trying to retrofit a home at a later date. The same goes for if you think you’ll want to age in place, may have mobility issues to grapple with, and if your family may expand or contract in the future.
How easy would it be to add onto your home design? Does the design lend itself to tacking on an additional module, or moving a module to act as a separate rental suite once kids leave the nest? Thinking about these things now can save you time, effort, and money later.
If you’ll be taking your home on the road, you will want to think about how this might affect your design. Are there modifications that will make it more aerodynamic and fuel efficient when you’re hauling it behind a truck? Are there features that won’t stand up to 100 km per hour speeds on the freeway? Will your home satisfy building permits in other jurisdictions where you might end up living? How about your chosen materials, such as insulation – will they be suitable for life in the desert and in the rainy Pacific Northwest?
Tiny homes and mobile prefabricated homes offer fantastic flexibility, but can end up being far less energy efficient and eco-friendly if they’re not future-proofed.
Consider climate change
This might sound a little apocalyptic, but the reality is that the climate is changing and a home that is suitable for today’s climate may be quite uncomfortable or downright dangerous in a decade or two. I live on the coast and often see beautiful waterfront homes for sale that I’d love to buy… if they were just a few more meters above sea level (and the water table).
Climate change will not only continue to raise the water table in many areas, making an earth sheltered prefabricated home particularly problematic, it is already causing more extreme flooding, tornadoes, hurricanes, droughts, and other weather events. If you build your home to rely on a certain type of renewable energy, microhydro or wind, say, only to have the climate scupper your plans in a few years, that can be a big deal for a little off-grid home, especially if you’re not proactive and hands-on.
Similarly, if you live in an area prone to tornadoes or hurricanes, a tiny home or prefabricated above grade, foundation-free design may be a terrible idea. And if you live in an area prone to drought and climate fires, this may affect how you think about rainwater collection and water waste filtration, as well as the type of insulation you use and other material choices.
Do you want your home to be certified green?
If you’re building an eco-friendly home just for yourself and your family and have no plans to rent it out as a resort, for example, you probably don’t need to pursue LEED certification or other green building qualifications. If, however, doing so will get you significant tax breaks or allow you flexibility to rent your place in the future, now is the time to put your processes in place.
LEED, Passivhaus, Net Zero, Novoclimat, and other green building standards have certain requirements for the completed home itself and for the construction process. You even get extra points for having a LEED accredited person on your design team! And you’ll need to ensure you have an environmental report showing how waste and recycling was handled during construction, as well as installing a heat and/or energy recovery system (HRV or ERV). There’s also the impact on your LEED score of choosing energy-efficient appliances and construction materials.
Some prefabricated home companies and tiny home providers do all the hard work for you, offering designs that qualify for LEED certification. Others may almost qualify but only if you choose certain eco-friendly upgrades.
One final tip for designing an eco-friendly prefabricated home: consider a design that uses SIPS. Structural integrated panels (SIPS) are prefabricated panels that typically consist of a foam sandwich, with the foam core integrated between two pieces of oriented strand board. Obviously, an eco-friendly home design is one that tries to avoid toxic foam products that contribute to global warming. Happily, some SIPS are now being built using such things as straw bale insulation or other greener insulating materials. And, because SIPS are made under factory-controlled conditions and can be fabricated to fit almost any building design, they offer serious advantages for durability, quality control, energy efficiency, and your building budget.
Prefabricated walls, panels, and entire modules of a home tend to be faster and less wasteful to put together in a factory before shipping them to your building site. Once there, they can be put into place quickly and easily, which speeds up your project and reduces the potential losses when materials are stored on site for weeks or months on end.
Do you have any top tips for designing an eco-friendly home? Is there anything I missed that you’d like to see covered here at ecoHome? Let me know in the comments below!