Drain water heat recovery.

Even after installing high-efficiency water heaters, low-flow fixtures, and practicing water-conservation habits, we're still faced with the fact that almost all our expensive hot water goes right down the drain. What a waste! Fortunately, I learned about Drain Water Heat Recovery (DWHR) devices from a friend who has been using this technology for over a decade, and was able to incorporate a DWHR unit into the barn. The drain water heat recovery system is basically a large heat exchanger designed to recover the heat from your shower water before it reaches the sewer system. The units consist of a large 3 inch copper pipe with smaller copper pipes wrapped around the outside. As your hot shower water drains through the 3 inch pipe it warms the pipe exterior. This heat is then transferred to the cold incoming water which is flowing through the smaller tubing wrapped around the drain pipe's exterior. There are no moving parts and nothing that can wear out- a very simple design and quite effective because there is lots of surface area and copper is highly conductive. By replacing a vertical section of your drain plumbing with the DWHR unit, a large percentage of the energy in the outgoing hot water can be used to 'preheat' the incoming cold water. I installed the DWHR pipe in a small vertical chase on the main floor to capture the hot water coming from the upstairs master bathroom before it goes under the slab. Putting the DWHR pipe in the basement would obviously be preferred, but since this is a slab-on-grade structure we don't have a basement- this is the only way I could incorporate the DWHR unit into the floor plan. I installed the GFX S3-60 model, which looks like this: Before testing it out, I insulated all of the drain plumbing between the sink, shower and the DWHR pipe. Before...

...and after. The insulating project is to retain the heat and also for sound abatement, since the bathroom is directly above the dining room. For this I used several layers of foam 'sill seal' material wrapped around the pipes and taped.Here is the vertical transition going into the chaseway:

I noticed most of the water noise was coming from the vertical transitions, so I insulated this area with XPS foam board and copious amounts of spray foam- not pretty, but it really cut down the noise and will contain the heat very well.

The building's incoming cold supply water (from our well water) always passes through the heat exchange unit on its way to the hot water heater, automatically extracting heat from the warm water running down the drain line. When I installed the DWHR plumbing, I added two gauges for monitoring the water temp going in, and coming out of, the heat exchanger: Today, I ran hot water through the shower to see how the DWHR would perform- results look good! With the shower running at 101F, the incoming cold well water was being 'preheated' from an initial 50F temp up to about 72F, capturing 44% of the otherwise down-the-drain heat! The manufacturer claims up to 57% efficiency is possible with this model, but that figure is based on a drain water flow rate of 5gpm- much higher than our low-flow sink and shower will ever provide. I'm guessing that around 40% is to be expected and is still very good. And the best part- the DWHR unit was virtually free- our electrical utility provider offered a $400 rebate for installing this $500 system, so the payback should be less than one year. Even at full price, this appears to be a very wise investment and a great energy conservation project. I'd be curious to hear what results others are having with the DWHR units.

The final steps on the yellow brick road.

It feels good to be actually finishing projects on the barn lately- this time its the yellow brick road. When standing in the original barn before it was deconstructed in 2007, I always felt that the brick floor gave the building a unique feel. Since the bricks were simply laid on the ground without mortar, it was easy to remove them undamaged, so we saved as many as possible. Some areas were heavily coated with oil and grease from decades of tractor parking, but the majority of the bricks cleaned up nicely using a pressure washer (thanks mom and Lisa!). To incorporate the old bricks into the new floor, I formed a meandering pathway across the new barn slab before the concrete was poured, which looked like this: After the structure was roughed in, I mortared the salvaged bricks into the recessed pathway- it soon became aptly named, the 'Yellow Brick Road". Since the bricks were laid with tight joints, I wasn't sure exactly how to go about the grouting process. Having absolutely zero experience with tile work at the time didn't help- so I decided to leave it 'as is' and come back to it later...that was 2008! Finally, almost two years later, I vacuumed all the debris out of the cracks (which amounted to over 3 gallons of sawdust and wood chips), and got started. I mixed some home brew grout using 2.5 parts sand to 1 part Portland cement- then with my mom's help we worked the powder it into the cracks using an experimental sweeping, rubbing and putty knife-packing technique. This worked relatively well, albeit very messy.

Working in sections, the dry grout was packed into the joint lines, then the excess was vacuumed off the top of the bricks and gently wiped clean with sponges. Once the bricks were fairly clean, I sprayed water over the dry mix using an HPLV sprayer to start the hydration process. We worked from one end to the other in this manner, taking an entire day to do the pathway. I gave the pathway a few more sprayings of water over the next few days, letting the grout set up. Then it required about a dozen moppings to remove the haze of grout that was all over the rough-textured surface (I had put two coats of AFM Mexeseal on the bricks before starting the grouting process, but it didn't seem to help that much). After alot of scrubbing, here's the nearly finished product:

The grout was VERY slow to harden using this method, and required some touch up in certain places where there didn't seem to be enough Portland in the mix for it to set. I changed the sand/Portland ratio to 2:1 for the touch up work and this seemed to be much better...more lessons learned on the rocky road of barn-building.

Heavy treading on the staircase.

Since the stair-building process has become a multi-year saga, let's recap. Starting with the timber-framed opening in 2009, I framed the curving staircase and built a border on the wall side using mostly reclaimed lumber and wainscotting. I milled slabs for the stair treads from some maple logs (these were from overgrown trees removed from the city streets in our nearby town).

The slabs were kiln dried over the winter, then cut into stair treads, planed and sanded smooth. A lot of precision cutting was required here, due to the unique shape of each tread and my choice to attempt a trimless installation. I finished them with Ecoprocote Eco-Tuff Clear Coat.

The final product:

I also made slab tops (these from white pine logs) for all the curved border sections.At the top landing, I built a small linen cabinet. The door pull was made from a hay rake handle that I found on the farm years ago (and saved for something like this). The stair treads have a variety of nail holes, knots, and worm holes to keep it real.

And finally, the treads were drilled for the motion-activated LED stair lighting kit, which is pretty cool in itself.

Final task is to fabricate a curved handrail...I'm still scratching my head over that one.

Solar Sundays Part VIII- getting closer!

*Warning* - this post is a lengthy, detailed description intended primarily for solar geeks. Proceed at your own risk.

The next step for the solar heating project was to install aluminum absorber plates to all the copper tubes in the system. When I built my prototype panel this spring, I stamped the plates myself. While this was a lot of fun to do once, the thought of pounding out a couple hundred more was not too appealing. Plus, I found a great source for high-performance pre-stamped plates so decided to buy them instead. These plates are made with an over sized groove which wraps around the copper tubing to maximize the contact surface and increase the heat transfer efficiency of the solar collector. They were also custom cut to my desired length, so all I had to do prior to assembly was paint the groove area with metal primer to prevent galvanic corrosion where the aluminum and copper are in contact. Time saved= lots. Normally, the absorber plates are fastened to the plywood backing of the collector framework, sandwiching the copper tubing in between. However, because I wanted a modular design that could be easily disassembled, I opted to build the fin-tube assembly separate from framework. I basically followed this design from the Build-It Solar website, with some modifications to work for my situation. I started by laying one of the copper tubing assemblies on a plywood work surface on the ground, then spacing it off the plywood with strips of 1" foam (I used the pieces of foam that were trimmed off when insulating the collector frameworks, but any thickness would work here).

Then a 3" wide strip of aluminum flashing was centered under the first tube, between the tube and foam strip.

Using a pair of modified Vice Grip 'clamps' (I had a friend weld these up for me, but they can also be purchased from the folks who made the absorber plates), the aluminum absorber plate is clamped tight to the copper tubing and held in position while a pair of sheet metal screws are attached at each end, through to the aluminum strip below. The foam strips underneath keep the screws from penetrating into the plywood work surface below. Next, the clamps are moved towards the center of the absorber plate and two more sets of screws are placed as shown. I found it beneficial to stand on the clamp with one foot to flatten out the absorber plate as much as possible before attaching the screws.

Then, repeat the process for three plates per copper riser... ...and a total of 24 plates per collector. Once the collector is finished, it could be lifted off the plywood work surface and the foam strips are easily peeled off the tips of the screws from behind. The result looks as follows- great contact between the aluminum and the copper! The finished assembly is light and easily movable. I also like that the fin-tube assembly is isolated from the plywood backer by the foam insulation in this design (less mass inside the solar collector is a good thing).

Two panels finished, seven more to go! Once all nine collectors were finished and connected back into the framework, I painted the whole system with Rustoleum High Heat black paint. The remainder of the bull work consisted of burying insulated water lines as well as power and communication wires between the solar array and the barn. I rented a Ditch Witch for a day to carve a trench about 150 feet across the yard. I was able to get about 30" deep with this machine- not below the frost line, but since the system will contain anti-freeze, it shouldn't be a problem. When the barn foundation was put in, I included a run of Thermopex under the slab and out into the yard about 20 feet. Now I needed to extend the insulated lines the remaining 60 or so feet to the solar array. Since Thermopex is around $12-$13 per foot, it was cost-prohibitive to use it again and I opted to make my own system (for about 1/4 the cost). I cut 1.5" XPS foam board into strips and glued them together using spray foam insulation...

...Then put a temporary board on top and clamped it while the foam cured.

The cured insulation assemblies (each 8 feet long) were positioned over the trench and 1" pex lines were placed inside before foam-gluing a cover piece over each one. I staggered the seams between the top and bottom pieces of foam for strength. Once the finished assembly was cured, I turned it on edge (it was too wide to fit in the 5" trench otherwise) and covered the top and sides with poly. The poly was taped around the insulation to hold it in place during installation. Finally, the wood cross members were removed and the pipes lowered to the bottom of the trench- it was a tight fit in places, but it worked!

I left a couple feet of pex on one end so the new run could be coupled to the existing Thermopex end using pex fittings. After the connection was made, I wrapped the bare pex with pipe insulation...

...and wrapped a slit piece of 4" corrugated pipe around that before covering the area with pea rock and landscaping fabric.

After pressure-testing the water lines, the trench was back filled with gravel to about the 4" depth, where installed a run of conduit containing a CAT5 wire and four T-stat wires.

FINALLY, the remainder of the trench was filled and pathways cleaned up- good as new!