SUPER INSULATED HOMES
Net-Zero is a targeted goal. It can be achieved through careful planning and several certification programs. Passive House is a certification standard, it has very specific targets and requirements. But what if you’re really into the ideas, but you’re not quite ready to commit to a certification program or Net Zero construction? Well then maybe a super insulated structure is for you.
Maine has some of the harshest winters in the US. We, along with a few other states, are in Zones 6 and 7 boasting temperatures in the negatives during our winter months. While Passive House and Net Zero are admirable and achievable, there are some things that should not be missed when building a new home. This is where we find super-insulated structures.
Some would say that sustainable building means you use local products. We are all for “buy local” but we think the most sustainable thing you can do when building a home is to reduce the demand that home is going to have on your time, your wallet, your comfort, and your health.
Super insulated structures with Mottram Architecture start first by maximizing the building envelope. It’s really difficult to change the insulation in a home after it is built. Adding granite counters, easy. Updating flooring, lighting, kitchens – easy. Digging old insulation out of wall with blocking, electrical, plumbing without completely gutting a home. Well let’s be honest, it’s not going to happen. So why is insulation always the first thing cut when budgets get tight? Because it’s not pretty, beautiful, you can’t show it off. It’s the least glamorous part of your building, but it’s 100% the most important. Let me explain why:
· Thermal comfort: As humans we only have a window of less than 8 degree temperature swings. So if the surface of the wall is more than 8 degrees cooler than the temperature we set our thermostat, we will consider our homes cold. In Maine with temperatures lowering to negative degrees in the winter, it’s critically important for our walls, floors, and roof to resist the exterior temperatures.
· Not only is it important for the insulation to resist heat flow, but the correct type of insulation needs to be used. There is a place for each type of insulation, and they are not all created equal. R-40 Fiberglass is not the same as R-40 spray foam or R-40 cellulose. They each have different air infiltration rates, are installed differently, have different environmental impacts, and require different fire protection. In a super insulated structure with Mottram Architecture you will see R-40 dense packed cellulose walls. Either double stud walls, or a combination stud/I-joist construction. You will see R-60 loose blown cellulose ceilings or R-60 dense packed vaulted ceilings. Basement insulation is often R-20-R-40 rigid insulation or ICF construction with an additional R-20-40 under the slab. Basement insulation is whole dependent on the site and type of foundation. Why do we choose cellulose over spray foam and fiberglass? Fiberglass, unfortunately has a very poor performance where air infiltration is concerned. Since building materials have a tendency to dry out and shift over the course of their lifetime, it renders fiberglass insulation a poor choice for exterior walls and roof construction. Fiberglass insulation also has a tendency to be poorly installed as it is very easy to stuff it behind wires, into small cavities and into joist bays. When fiberglass insulation is compressed, it looses R-value. Spray foam, on the other hand, has very little air infiltration and is great to seal gaps and cracks. However, as buildings shift and dry out it can get pulled away from the structure and allow air paths though the structure. It also has some less favorable environmental agents used in the product and installation agent. Spaces must be ventilated for 24 hours after installation, it smolders when it burns so it must always be covered, and it’s potential to off-gas after installation is still being questioned. Cellulose, is not 100% fool proof. If it gets wet it can hold 130% of it’s weight in water. But that is it’s worst fault. It is treated with boric acid, and therefore does not burn. It is made of recycled newspapers and is 70% recycled content. And due to the contents of the product, it is almost always made locally. When dense packed the air infiltration rate is very low improving the airtightness of a building, and because it is loose, it will move and shift with the building as it dries out and adjusts. For these reasons, cellulose is always our first recommendation for Maine.
· Advanced framing techniques. We recommend 24″ on center, insulated corners, and engineered framing to reduce the amount of lumber found in our walls. Simply switching from 16 to 24 give us a framing factor of 16% instead of 25%. 9% less lumber means a lot more thermal resistance! Offsetting the cost of lumber with insulation is one of the best choices you’ll make.
· Continuous, uninterrupted insulation removes thermal bridging from your wall system. Thermal bridging is areas of construction that have a low R-value and translate cold from inside to outside. Wood has an R-value of 1 per inch. Cellulose has an R-value of 3.3-3.5 per inch. If your wood stud touches your exterior sheathing and your interior drywall it is 3x less effective then your insulation. These cold sections of wall will be the first places you’ll see condensation and then mold growth. It’s also why we notice the floor is cold along the baseboard, or the trim is cold around the windows. Eliminating as much, if not all thermal bridging, like passive house, leads to more durable homes that are more comfortable to live in.
In our super insulated structures, although we are pushing high R-values, advanced framing, and reduced thermal bridging, we realize that these customers may not be the triple pane windows from Europe type customers. Although we will try to encourage you to put in the best windows you can afford, we will work with you to properly locate windows so you can reduce and eliminate windows that you don’t need. We spend a lot of time during the design phase helping to orient the house on the lot, use strategic windows to take advantage of the view, place them close to the ground so spaces feel larger then they are and your connection to the outdoors is magnified. We do what we like to call, daylight planning, where we place the rooms in the home adjacent to the sunlight that would be most beneficial for each occupant. Do you like the sun to rise in your bedroom? Do you want to watch the sun set from your kitchen. And most importantly we group the utility spaces on the north side of the house to buffer the coldest side of the home.
Our super insulated structures also allow us to reduce the size of the heating system for a home helping us to offset the cost of extra insulation. We always take into consideration high quality indoor air and provide proper ventilation for the occupants of our homes. And last, but never least, we consider the environmental impact of the building components we are using so that we do not trap harmful or unwanted contaminants within our homes. These home should be happy, healthy, and beautiful!
If you love all the ideas of the principles we mentioned above, but you’re less concerned about understanding all the ins and outs of the science. (Since that’s our job, and really what else are you hiring us for! ) Then this is how you move forward with Mottram Architecture on building your dream home.
Answer these questions:
We don’t require any information for you to reach out to us about your project. But during our first phone or email conversation we will ask you the following questions, so it will help if you have thought about these before you contact us.
· What are you looking for?
· Why do you want this?
· On a scale of 0-100 how motivated are you to finish the project?
· What is your budget for this project? Or do you need help determining what your budget should be?
· When do you want this project to be complete?
· Apart from you, who else is involved in the decision making process?
Once you’ve answered the questions, give us a call. We do an initial 1HR consultation at no cost to you. It’s a great way for us to introduce ourselves, go into more detail on who we are and how we work, and find out your project budget, scope, schedule and really what you need from us.
After our first introductory meeting, we will put together a proposal for you on what it will be like (and cost) to work with Mottram Architecture based specifically on your project.
If you’ve read “super insulated” and “passive house” with Mottram Architecture and you think “Yeah, maybe that’s for me” but you think “I could do just a little bit better” then maybe Net Zero is for you?
Similar to super insulated homes and passive house homes, a Net Zero home with Mottram Architecture is going to have similar principles and expand on those to achieve Net Zero. What we, at Mottram Architecture, deem Net Zero: The home produces all the energy on site that it needs to operate each year. There are complicated metrics about homes that are connected to the grid vs off grid homes. If you choose to participate in a Net Zero program we will help you achieve all the requirements of that program. If you want to be Net Zero without a program we are going to help you produce more energy than you use at the end of the year. It may mean that you produce more in the summer and feed back into the grid, pulling electricity from the grid in the winter months. Or, it may mean that your solar array produces enough energy year-round to be off the grid entirely. These are the principles that we use to develop our Net Zero Homes in Maine:
· First we will visit the site and help to place the home for optimal solar exposure. Whereas in Passive House and Super Insulated structures, it’s good to face south, in a Net Zero home it’s imperative. Although you could do a ground mounted solar system or maybe you have access to wind power, the best and most viable solution to Net Zero construction is the ability to produce power directly at the source.
· Second, after orientation is determine we will maximize the building envelope. With Mottram Architecture you will see R-38-40 dense packed cellulose walls. Walls are either double stud walls or stud/i-joist combos. Ceilings are R-60 loose blown cellulose or R-60 dense packed vaulted ceilings.
· All structures will have one continuous air barrier. This is achieved with a number of tapes, skins, vapor barriers that are all connected together to reduce air infiltration through the building components to increase durability and through the building envelope to reduce heat loss. The continuous air barrier also reduces drafts which decrease occupant comfort. It’s no wonder that we only own our homes for 7 years in the US before we trade up for newer, bigger, prettier, only to not understand why we don’t continue to love our spaces. If you’ve ever been through a Net Zero home, you may start to understand that it’s not just how beautiful the space is, but how comfortable it is to be in, how does the sunlight lift our moods, and where are all the components that make the home truly unique for you and your family.
· Healthy Indoor Air Quality – In order to really achieve a Net Zero home it’s important to reduce air infiltration. Any energy that needs to be used to keep a home comfortable just increases the size of the solar array which increases the budget. At some point it will become cost prohibitive. So a concentration on reduction of the thermal envelope and the air infiltration means you need to pay attention to the air quality within the space. Heat recovery in Net Zero homes in essential in reducing the demand. Everything in Net Zero is a balancing act. You need to provide fresh air and run the fans that provide the fresh air, but reducing infiltration reduces the heating system which also needs to be run by the solar system.
· High R-Value/Low Infiltration windows. As we mentioned above, everything comes down to demand. The higher performance the windows are, the less energy you need to make with your solar system. That being said, it’s not impossible to achieve Net Zero with double pane windows, it just requires more energy. Triple pane windows improve the occupant comfort because the interior surface temperature of the window is higher and the construction allows them to seal tighter and let less air through. But most important with windows is the right type and operating style. A fixed window will have the least air infiltration, followed by casement, double hung, awning and hopper, and last sliders. If you can reduce the number of windows you need, place them in the right locations, only have operating sections where needed you can make a huge impact on the performance of your building and reduction of energy demand on the solar system.
· Heating system. With Mottram Architecture we are 90% likely to recommend a heat pump for our Net Zero homes. First, when we talk about Net Zero we talk about our ability to produce all the energy on site that we need to operate the home. The most effective way to create energy on site is electricity. Secondly, electricity has no fossil fuel off-gassing that can be trapped in a super tight home and cause serious harm to occupants. Third, heat pumps are significantly more efficient than standard electric heat. Depending on the configuration of the home will depend on whether it requires a ducted or mini-spilt system.
· Efficient water heating technology – typically this can be a hybrid heat pump hot water tank if you have an unfinished basement or garage. If you are building a home on a slab, more likely you will have an all electric tank or a solar thermal system with electric back up. If you are a home that uses gas, we may have an on demand modulating condensing boiler that would produce your hot water. As we mentioned before, gas is not a renewable resource and it can get tricky offsetting the use of fossil fuels in a Net Zero home.
· Renewable power production: To truly be Net Zero we believe a home should produce more power on site than it consumes during the year. On site produced energy is most efficient when it is directly attached to the structure which is using the energy. In Maine that means solar. By following all the principles above we can reduce consumption of the home to a manageable amount of energy use that can be produced by a solar array. Most people are not interested in being off the grid, so a grid tied solar system which produces more energy in the summer and pulls from the grid in the winter is the most cost effective solution. This allows you to put a smaller solar system on your home since you can achieve peak demand in the summer and count your credits for over production towards your winter months. If you size a solar system to be completely off the grid it will need to meet peak winter demands and will significantly over produce in the summer months. The risk with completely off the grid systems is that we have yet to figure out how to control the weather! If we have a cloudy month with snowfall and covered panels you may need to seriously watch your electric consumption and make trade offs so you do not run out of power. This is where you may need to forgo making coffee, watching tv, or even in severe cases, taking showers. Therefore, most customers choose to stay tied to the grid to safely enjoy creature comforts.
