Prepping the Foundation Before Foam.

Thermal bridging through foundation walls can lead to significant energy loss/gain in any building, whether super-insulated or not.  There are several options available to decrease thermal bridging through a concrete foundation.  An insulated concrete form (ICF) is one of the first products that comes to mind to mitigate energy loss/gain through concrete.  We decided agains ICF mainly because the footings have to be pretty level in order for the forms to be level.   In a poured concrete wall, if the footings aren't perfectly level, a reference level can be maintained inside the concrete form panels by attaching a 2x4 and levelling using a transit all the way around the form.  Once the concrete is poured into the form, it is levelled to the bottom of the 2x4 giving a perfectly level wall once the forms are stripped.   Since this is a common local practice, it seemed like a good place to start.  Adding EPS insulation on the exterior of the foundation for the whole structure (although not necessary for the garage/porch) and the interior foundation walls for the house then creates a kind of poor mans ICF.

The forms used for pouring the foundation are reinforced with steel straps and have clips that join adjacent panels.   The interior and exterior panels are the joined together with a reinforcing rod which keeps the panels from splaying apart once the concrete is poured.  Once the forms are removed it leaves a steel connector protruding through the concrete as well as a knob of concrete which gets in the way of applying exterior foam (Picture 1 below).  Each steel connector can be removed with a swift blow from a hammer.  However, usually a knob of concrete remains intact (Picture 2).  I have found that using a masonry hammer at the right angle and applying a swift blow from a framing hammer to the masonry anvil breaks it off in once piece.  If not some minor chipping is required.  The concrete flies everywhere so you need to make sure that your safety glasses are on!

The broken steel rod provides a way for water to enter the foundation and can rust the connector rod. Traditionally, people have patched this with plastic cement.  Its a simple cost effective solution (Picture 4).  There are very few local options for water/damp proofing the foundation.  Nobody sprays special coatings and stick on membranes are typically special order so I opted for locally available products in order to keep things simple.  We decided to use ResistoSeal Foundation Coating (or equivalent) which is a bitumen based sealer which hardens once the solvents evaporate (Picture 5).  Its hardly a green product but it is a cost effective option that is readily used by local builders.  Nobody said this stuff is fun to work goes everywhere!  Being next to the 3rd windiest city in the world (St. John's) makes this stuff drift horizontally as you are lifting your roller from the rolling tray.  Needless to say, my father and I got suited up in disposable tyvek suits before opening the first bucket because we knew what to expect.  Disposable gloves and old boots were a necessity.  Although dry, the air was cold and so was the foundation....2 deg C!  The buckets of sealer were kept at my house until we needed them because it became so hard to roll once the liquid became thick. In fact, you could feel the resistance on the roller almost immediately after the roller touched the cold concrete wall.  Despite being cold, 4 hours later, we were all done!  The section we had started with wasn't tacky anymore and was drying nicely.

The footings are also slated to be brushed with this sealer.  Brushing became near to impossible because it was too cold.  Tomorrow will be 11 deg C and sunny....better than this grey foggy day....

Picture 1.  Knocking off steel connectors used to connect concrete forms.  

Picture 2. Chipping away a knob of concrete left from forming.

Picture 3.  Chipping complete.

Picture 4.  Filling connector rod holes with plastic cement.

 Picture 5.  Bitumen based sealer.


  1. Been a while, so some catch up on your many photos and writing. Wonder why you use epoxy instead of grout for the rebar......
    Your basement concrete looks a good job. You may be surprised at my cottage add on 5 years ago. I was on fairly solid ground, about 12 in of topsoil, and avoided a tear up. I manually (pick and shovel) dug a trench 12 in deep, put 2 inch rigid foan both sides into the trench and poured concrete into for 8 inch wide, but put 4 pieces of rebar continuous, just in case frost got under, the concrete would not crack. Actually worked well for me, although if the house was not continuously heated , frost may get under it. I did see inside temperature in an unheated room at about 36F ground, but where heated gnd about 50 f in winter.
    This method was not up to code, naturally, but with 4 in of foam, is pretty effective, and low cost, and no landscaping to do. May not have worked so well 30 years ago, but frost no longer runs deep here.
    Like your photo of the boat. For wind generators on our grid, capacity is limited generally to 10 percent of our hydro generator capacity. Few understand why......but is apparent from the operation of the putt putt engine.......just wonder if you are aware of the reason for you are pretty technical, but may not have crossed your mind.
    I could say you should have waited for warmer weather to start..........but that may take to mid August.
    I sometimes wonder (given our location) if in 30 years we will have this weather year real winter nor summer, just 12 months of Apr/May stuff! . I think the caplin and cod noticed the trend 25 years ago, and moved off.............
    Winston Adams

  2. Hi Winston,

    Good question. Grout is almost impossible to squeeze in the hole. Additionally, grout needs to stay wet in order to set properly. The surrounding concrete would wick the grout out of the cement pretty quickly. That being said, the product I used is an epoxy that is formulated for fastening/anchoring to concrete ( It is twice as strong as concrete and sets up in about 10 minutes. Once the hole is half filled, you push the rebar in slowly and it squeezes out around the rebar forming a locking seal to the rebar and concrete.

    The low cost of adding foam to the concrete inside and out makes the insulation a great investment to deal with thermal bridging. Its much cheaper than ICF. Not sure how long it will take but we are starting today and I will update the blog when it is completed.

    I have heard the argument that power generation works better for sustained winds. large power turbines naturally have two properties working against them. One is inertia, the other is the magnets/coils used to create electricity. The current created by the generator naturally creates a magnetic field which resists the magnet that created it (Lenz's Law) that acts as sort of a braking system. The wind speed needs to be large enough to overcome the inertia and large enough to overcome the second effect. Once spinning there is no problem unless the wind speed is too large then turbine either brakes or I have seen turbines which can change the pitch of the blades so the RPMs remains constant. With sustained constant wind speed there are less interruptions in power. This is what I have surmised, although I am sure there are also other the government not wanting to use renewable energy in light of it taking away profits from muskrat falls. This past friday, the PUB announced that net metering will become reality and the will start accepting applications after July 1st. The funny thing is that they have capped generation at 5 MW total for the whole province......its a start but a bad one.

    Waiting for warmer weather is like playing a game of blackjack around least Im heading into the summer!

  3. Yes, Nfld has enough wind power to supply all of Canada, but the variable speed of wind makes it difficult of to keep 60 cycles per second,which it much to be synchronized with our power grid frequency. The big generators, hydro or thermal can weight hundred of tons, while the wind generators, a few tons. So, the small inertia of the rotating mass of the wind generators is not that stable. The tolerance of frequency is about 1 cycle, so say 59 or 61 per second. Those who suggest adding 600MW of wind or more ignore this stability issue.
    The inertia principle, as you mention, is very apparent with the old Acadia, with the big cast iron wheel external to it. Always amazed how it seems to almost stops but keeps running at low speed because of the wheel inertia. Whereas modern outboard motors run like crazy, and cannot do that slow run speed, with little inertia. Because of this, our grid could handle 200 or so MW of wind, a fraction of out large mass generators, without risk of stability of the frequency, and blackouts.
    Oh , if your foam joint is exposed any.......insects can cause damage over time, I have noticed, and I saw mice nest under buried SM foam,that was there for 20 years, and chewed it up some, where part was not fully covered by soil, they dug under, and enjoyed the warmth.
    Your efforts for small checks against energy loss may seems a waste of time and effort to some, but such efforts are accumulative, as you are fully aware, for overall good results ......that last decades. And so you are a bayman.......always an asset.
    Parts of India reached about 50C today, which translates to 122F.........about the temperature of my hot water do they live, without burning their fortunate we are here, just a bit chilly.


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