The floors in my home are all the same… 4 inches of concrete with radiant heating pipes.  This is a big part of producing some major efficiency in my design.  I try and follow the mantra that everything I put into the home has to do more than one job.  The floors score really high on this count.  The concrete floors are the finished floor surface, the radiant heating system and thermal mass.   Polishing the concrete floors is relatively new in Canada but I’m told it’s very common in the States.  I’m not sure why but I think it might have something to do with the fact that so many homes in the States are slab on grade while our homes almost always have basements.  Having to deal with a concrete main floor I think is a big reason why concrete floors are an attractive option for our friends to the South.

Polishing concrete is a lot like sanding wood.  You start with a course grit and you work your way up to a fine grit.  Pretty simple.  In my case, I start with 50 grit followed by 100,200,400,800,1600 and then 3000.  The floor polishing machine has 3 8inch velcro pads that spin while all 3 pads rotate in a planetary motion.  The result is a random scratch pattern that leaves a smooth, scratch free surface.  Up to the 400 grit, you add water to the floor periodically.  The water is held in a container built into the floor polishing machine.  There is a handle which you pull occasionally to let water pour into the sanding area.  I usually go for 20 minutes or so before I stop and vaccuum up all the water which is now like a thin chocolate milkshake.  I overlap the passes 1/4 or 1/3 and continue painfully slowly until the entire area is done.

The remaining grits are done dry.  There is no dust to speak of but it’s probably still a good idea to use a dust mask.  Alternatively you can hook up a vaccuum directly to the polishing machine - I’ve found that to be too restrictive.

After the 1500 grit the floor is getting a nice polish to it.  You have no trouble seeing a fairly clear reflection of lights or items in the floor.  Now is the time to add any stain to the floor for colour.  Basically, this is a mixture of water and acetone and dye which is rollered or sprayed onto the floor.  Once this is dry, you can buff the floor with a floor buffing pad.  Now you add a densifier which is a chemical that reacts with free lime in the concrete to form a much harder, denser surface than concrete alone.  A quick repeat run over the floor with 1500 grit brings an even better polish to the floor.  A final run with 3000 grit and the floor is looking pretty sweet.  A quick application of a penetrating sealer and your floor is ready for thousands of people to walk over your floor with no maintenance other than a damp mopping once in a while.

The Latento Solar Storage tank is an interesting development in solar space heating (www.latento.de).   Essentially, it is an unpressurized 500 litre tank which is filled with water and optionally some phase change material (20 kgs of wax).

Latento Cutout

There is a series of heat exchangers mounted in the tank to put energy in or to take it out - the water in the tank is for heat storage only, this water is not circulated out of the tank.  It has a number of features that make it a suitable choice for solar space heating in some applications.   First, it tries to maximize solar gain by putting the solar heat exchanger at the very bottom (and coldest) part of the tank.  There is an inverted funnel and pipe which surrounds the solar heat exchanger and lets the solar heated water gently rise up through the tank without disturbing the delicate stratification.   There is a very long ribbed stainless steel heat exchanger that coils around and around the inside of the Latento which provides for a version of instantaneous hot water heating. That is - cold water enters in one end and by the time the water comes out the other end - it’s hot enough for a DHW supply.  I found that when the tank temperature was above about 42 degrees C , the water was hot enough that the wife didn’t complain that the water was only lukewarm.  There are two other heat exchangers, one is used to extract heat for space heating and the other is connected to a backup boiler for reheating when the solar gain is not sufficient.  Another interesting feature is a copper pipe which runs vertically from the bottom of the tank straight out the top.  The bottom of this pipe is capped off.  This pipe allows you to insert temperature probes to any depth in the tank to get an accurate reading of the particular layer you are interested in.  After the probe is inserted, the pipe is filled with fine sand to hold the probes in place and to make good thermal contact.  Remember that this tank promotes stratification so every vertical inch of this tank may have a different temperature.

My goal is to create a completely solar heated home.  If it’s cost-effective and practical here in Calgary’s hard climate then it should be done everywhere.  Spring is fast approaching and I have plans to begin this project in stages with the final installation before the beginning of the next heating season.

It will take up to 40 evacuated tube collectors to do the job and this is too many to mount on a roof so I’ve begun by leveling a spot just to the east of the home where I will have two rows of 10 collectors each.  The piping from each of these two rows are one inch copper pipes.  Each row of collectors will be 5 parallel sets of 2 collectors in series.  Though the selection of PV powerd pumps is limited, the best choice seems to be small pumps made by laing (http://www.lainginc.com).  As unconventional as it is, it will take 3 of these pumps in parallel to supply the 5 gpm through each row of collectors.  Yes - that’s right 6 pumps instead of 1- if they made a suitable pump that could do the job on it’s own I would use it.  Although these pumps are supposed to be very reliable (50,000 hrs Mean Time Between Failure MTBF) having several gives me some added redundancy.

Initially, I will do a test with 4 or 6 collectors to see how the balance of the system operates.  I’ve been doing some performance testing of various brands of solar thermal collectors and it makes sense to pipe the heat into the house instead of wasting it outside as I had been doing.  I’ve built some simple hangers to get the 4 solar supply/return pipes from the east wall of the house over to the mechanical room where they will tie into my hydronic distribution system.  To start with, I will be using a Latento solar storage tank (www.latento.de).  This has been plumbed into the low-loss header which was installed with my original boiler system.  I added a couple of relays and a differential controller which will pull heat from the solar storage if it is hot enough or fire the boiler up instead.  Of course, the idea is to completely avoid the use of the boiler when the solar system is completely up and running in its full glory.

Incorporating a place in the home for long-term storage of vegetables grown in the garden makes a lot of sense to me - after all - wouldn’t it be ironic to build a home that supplies all of its own electricity and heat and then starve to death because you had no food?  The ground temperatures in my area are around 5 degrees C which is about the same temperature as a fridge - so it’s a good temp for long term storage of many of the kinds of vegetables that I’m able to grow in my area.

I incorporated a root cellar right into my home design which lets me have a root cellar - or cold room as they are also called convieniently accessible from my basement.   It is about 6 feet wide and 14 feet long and  I have a standard exterior grade door for access from a storage room.  The room is constructed against the outside of the home and is made from the same materials as the home itself - ICF walls consisting of 4.25 inches of EPS foam (each side) sandwiching 8 inches of concrete.  The roof of the root cellar is also the concrete pad leading up to my front door under which I added 4 inches of EPS foam.   You would not know from the outside that there is a cold storage in this home.   The only clues are two 4 inch vents that I integrated into the side of the home which allow the cold cellar to breathe.   After adding and compacting fill and sand, we tiled the floor with 18 inch black patio blocks.

The entire inside surface has an acrylic stucco basecoat over which I’ve painted a flat acrylic white exterior latex paint.  I was originally thinking of a final coat of clear epoxy - which I have 4 leftover gallons of - but the possibility of moisture getting behind the epoxy and causing it to lift off in an unrepairable mess has caused me to rethink this approach in favour of just leaving the breathable white acrylic latex as a topcoat.  It will not be as neat as having a completely smooth and easily washable epoxy surface, but I think it will prove to be the wisest choice in the long run.

This story demonstrates that even a highly efficient boiler can still have major opportunities to improve overall system efficiency.

Viessmann Boiler

At one point I was interested in determining where the electrical consumption was happening in my home. I used a kill-a-watt meter to measure the electric consumption of devices that plugged into a regular 120 v outlet. While making my way through the mechanical room I noticed that my high-performance Viessmann boiler also needed to be plugged into a regular 120 v outlet. So I plugged the energy meter in and was surprised to determine that the boiler pump was running 24 hrs a day. At 130 watts, this comes to 130watts X 720 hrs/month = 93.6 kwh. This is around 20% of my average monthly electricity consumption!!!

I spoke with my plumber, the local Viessmann rep, and the Viessmann technicians at their Canadian office in Ontario and initially didn’t get much initial interest as to why this was something to worry about. I was more or less told that this is the way the system is designed and it’s working like it should. Well, in my case, building an energy efficient home, where the idea is that the boiler spends more time idle than in heating mode - it doesn’t make sense to pay for unwanted energy consumption. Eventually, I found a sympathetic Viessmann engineer, Richard, who understood my concern and recognized that this was a problem. I think it was also Richard who relayed a story to me that he had heard of a lady in Germany who was complaining also that her boiler was consuming too much electricity on standby. In her case however, she had a solar system supplying her home and the entire output was ending up just supplying the pump!! This is plausible because a 1kw solar pv system will produce around 100 kwh/month. Can you imagine spending $10,000 on a PV system just to break even on your boilers’ (mostly unneccesary) internal pumping requirements!!

Ok. So whats the deal? Well the pump will run 24/7 when two conditions are true. The first is that you have space heating selected on the front of the boiler. The Vitodense 200 has 2 modes: one is for DHW and the second is for DHW and space heating. Although it’s not practical for winter operation, you could select DHW production only for the summer months when you know you will not require space heating.

The second condition is that the outdoor reset control senses that it is more than 16 degrees C outside. In this case, the boiler assumes that the very minor heat loss of the house during these conditions will be offset by the homes internal loads and residents.

After another impassioned plea to the Viessmann engineers, they came up with a solution to exploit the second condition. Essentially, they recommended a SPDT relay that is used to alternately switch between my regular outdoor reset control sensor and a second outdoor reset sensor mounted inside the home where the temperature is greater than 16 degrees. Not a bad solution except that an outdoor reset control sensor retails for about $100. A quick check of the Viessmann manual revealed that the outdoor reset control sensor is a thermistor whose

resistance/temperature is shown in a graph. I selected a resister with a value of 560 ohms to simulate and outdoor temperature of about 30 degrees C. How does the relay know when to switch between the two sensors? I’m using a Taco relay control panel to switch my floor pumps on or off and this device has an end-switch that is essentially just a spare relay that energizes whenever any of the floor pumps turn on. This way, when there is a demand for heat (ie. floor pump turns on) - the relay switches over to the outdoor sensor and when there is no demand for heat (all floor pumps off)- the relay switchs over to the resister which fools the boiler into turning off his internal pump. How much this strategy will save me depends on the ratio of when my system is in heating vs non-heating mode. In the dead of winter this might be 50% of the time and in the summer this would be 0%. It is no longer neccessary to switch the boiler over to DHW mode only for the summer.