How do I insulate my foundation and how much is enough?
Insulating a foundation is an important step in both retaining heat during the winter and reducing heating costs. Concrete or concrete block, the material used to build most Alaskan home foundations, is very conductive. If not insulated, it will transfer heat from a crawlspace or basement directly to the surrounding soils or outside air. Many Fairbanks homes, especially older homes, do not have insulated foundations. Putting insulation on the outside of the foundation will slow that heat transfer and ultimately save energy and money. The most commonly used insulation for new homes and when retrofitting older homes is rigid foam board that is rated for below-grade application. If an insulation is rated for below grade, that means it is less susceptible to water absorption and is not damaged as easily. Another option is to hire a professional to apply spray foam to the foundation, which has similar insulative and water resistant capabilities.
In 2010, building code required that new homes had R-15 of insulation installed on a foundation. That amount is equivalent to about three inches of rigid foam board. Insulation should be applied to the outside of the foundation all the way down to the footer.
Spray or foam board can also be applied to the interior foundation or crawlspace walls. This method saves effort because the entire perimeter of the home does not need to be dug out; the down side is that this method consumes interior living space. Be sure that any interior insulation is either fire rated or is covered with a fire rated surface.
My home is starting to settle a little bit. What advice can you give on leveling a house?
What is an acceptable amount of settling is a relative question, but if windows and doors start to bind that is a good sign that things have gone too far. Plumbing systems can also be at risk for damage and are often overlooked until it is too late. One option to level a home is to use hydraulic bottle jacks. If you can get under the beams that support the house and raise them with bottle jacks, that is a fairly inexpensive route to take. Some home moving companies and contractors will have airbags that they gradually inflate under the home. As the building comes to level, they will add more structural support to the structure. This approach works well on soft soils. One older method involves a railroad jack, which relies on a mechanical ratcheting system instead of hydraulics. This device can fit into a four-inch space, making it very handy. A few of the rental stores in town still have this jack.
The act of raising a house involves potentially lethal amounts of force and weight that can react in unpredictable ways. Relying on a jack to support the structure while working in danger zones is extremely risky. There should always be some fixed means of support, such as cribbing in place to support the structure, should the jack fail. Alaskan home owners are renowned for their “do it yourself” attitude, however sometimes house leveling should be left to a professional.
I am going to dig up my foundation this summer so I can put on outside foam insulation. Do I need to clean off my foundation in any way, how far down should I dig, and how long will the ground be frozen?
If the foundation has not been waterproofed, or the product that is installed needs some touching up, then clean the area thoroughly. In the case of cement block or cast-in-place concrete, cleaning will probably involve hosing off the foundation, letting it dry, waterproofing it, then adding the insulation. For waterproofing, apply a peel-and-stick membrane or a waterproof foundation coating. Be sure to follow the application instructions carefully. These membranes work well for both new construction and retrofits, but the concrete must be clean first. If your foundation already has good waterproofing, then dig away the dirt, brush off the foundation and place the foam tight against the wall.
In terms of how far down you should dig, remember that heat always goes to cold. Where you have a temperature difference inside to outside, you are going to have heat loss. The bigger the temperature difference, the more aggressively the heat will try to escape. The frostline in Fairbanks goes down roughly four feet on average. Some winters, that frostline goes much deeper. Below the frostline, there is an average soil temperature of 32 to 40 degrees. A good practice is to apply rigid foam insulation that is approved for direct burial, all the way down to the footings. In 2010, Fairbanks building code required three inches of thickness for foam below grade (below the soil).
Good resources for finding out when the ground has thawed would be the local excavation and septic companies. They work in locations throughout the area and may be able to help you predict the thawing time for your location. June is usually a good month in which to begin excavation, though if you are on the north side of a hill, in a heavily shaded area, or have wet soils, your ground may behave differently.
Is there a way to tell if land is full of permafrost just by looking at it?
There are some visual indicators, but they are not 100% reliable when determining whether or not land has permafrost. For starters, look at the other houses in the area and the types of foundations they have. If there are a lot of houses on posts, or if houses with conventional foundations are sagging, that could be a sign of permafrost. If the land is down in the flats or on the north side of a hill and has mostly little black spruce trees and moss, that often indicates ice in the soil, because the land cannot support a big root structure. Sometimes a piece of land can have good-looking ground but permafrost underneath at a low depth or ice lenses (pockets of ice) only under small areas.
If you’re going to build on permafrost, what things do you want to keep in mind when preparing the site?
Minimal site disturbance is the accepted practice. Often people want to scrape off all the trees, all the brush and everything else, and get down to clean dirt. This is typically what you do with good soils and it seems like the most appropriate practice because it’s easier to work on, easier to put a road in, etc. However, it’s typically the exact opposite of what you should do with permafrost soils. The trees and the groundcover are your best friend. They protect and insulate the ground from the heat of the summer. A great example is the green moss that you find in a lot of the low-level areas in Fairbanks. Moss has a high insulating value, and if you move some of that, you can dig down a couple of feet and a lot of that ground may be frozen in the middle of summer.
One thing that’s common now with roads and gravel pads for foundations, is a layer of geo-textile fabric that goes down on top of the groundcover. The fabric comes in rolls about 12 to 18 feet wide and is designed to cover a roadbed. It’s super tough, and when you put your tailings and fill down, it helps bridge irregularities in the ground and small areas where it settles.
One older, now less-used method is to take all the trees and groundcover from the site and stack it crosshatched in the roadbed. So you’re getting your own, natural, inexpensive geo-textile fabric to support the road above.
When it comes down to it, clear only as much trees and ground as you need to. However, you’ll have to balance that out with fire protection. Be aware of drainage. If you want to keep your home out of problem areas, build up high or some place where you are avoiding a natural gully or natural drainage.
Over the life of my home, what advice can you give on keeping permafrost from causing problems with my foundation, or my property in general?
Good drainage will go a long way. Direct groundwater away from your foundation, whether it’s from spring melt or rainwater. Gutters will help. Downspouts should kick out from the building five or six feet to make sure water doesn’t pool around under your house.
Good shading is also very important. There are a lot of was you can keep direct sunlight from hitting around the house, or near the house where it can start thawing the ground. You can do this with large roof overhangs, planting or keeping extra trees, or even having a wrap-around deck.
A typical foundation should be insulated on the inside or outside to avoid heat transferring to the surrounding soils. Many Fairbanks homes have exposed concrete foundations, which transfer a lot of heat. Even if you are not melting the permafrost around your house, you are losing substantial money through the walls of your foundation. Properly insulating will save you a lot. If your house is built on pilings, make sure you have good airflow under there. You don’t want to store too many things under the house, or put on a skirting that is going to trap air that leaks from the house floor.