Drainback Solar Heating System

There are two types of solar heating systems appropriate for cold climates: glycol and drainback closed-loop systems. We chose to use the drainback system because it best fit our application. Rather than explain this system myself, I think this is the best internet site to begin learning the details involved in it. Our system is essentially designed on the same principals found at this site. However, our system only has one tank, which acts as both the drainback tank and the storage tank.

The article found at the referenced link explains that a drainback solar water heater is not able to provide 100% of the hot water we will need. So we have paired our system with a tankless heater. This will provide any additional heat we may need on the coldest and cloudiest days in Torrey.

This is the mechanical room for both the culinary water and the radiant floor. Heat for both will be provided by the drainback solar heating system. The tankless heater that provides any necessary supplemental heat is the gray box in the upper right hand corner of this photo.




For us, the negative aspect of this whole system was the type of solar panels we could use. As you can see, they are big and architecturally unattractive. The fact that we will ultimately use minimal propane for heat resulting in very small utility bills, will make them more and more attractive as time goes by. With a closed-loop glycol system, it is possible to use panels that can be mounted flush with a roof, but the glycol system appeared unworkable for what we needed.

I did have to laugh a little when reading one internet site that said, "... the drainback solar system is relatively cheap and simple to install and maintain." I'm just not quite sure what it's cheap relative to.

Solar Heating System

It’s funny how ostensibly minor events are, in truth, milestones. Today that small event was a drive to the post office to mail an envelope containing the documentation showing our solar heating system is now installed and working. It’s the details that led to this moment that paint the larger picture.

Detail number one: In early May of 2010, Wayne, our architect, visited us in Torrey for a few days in order to help us work on our timber frame. Serendipitously, during that week, Phillip, our plumber stopped by our yurt to discuss the installation of the water tank for our solar heating system. Because they both happened to be there at the same time, they sat down together and devised a much-improved plan that would store our hot water in an underground tank and would preserve storage space inside our house.

Detail number two: Not long after, Dura Crete, a Salt Lake company, manufactured that water tank and delivered it to Torrey where it was easily installed in a hole beside our house. On the same day, Phillip and company completed that portion of the solar heating system by, among other things, placing copper heat exchangers inside the tank.

Detail number three: At the same time, Scott, Doug, Shanna and I laid out the PEX tubing which will allow the hot water from the buried tank to circulate throughout the house providing heat when we need it. Once that was done, Tyler and crew poured our cement floor.

Detail number four: In August, we raised the timber frame and built the porch in September and October.

Detail number five: Tyler’s crews spent any time they had between jobs from October to the first week of January building the roof to the point when Scott would be able to blow in 10,000 pounds of insulation, which he did from January 11-14.

Detail number six: The weather was cooperative so, once again, Tyler and crews ? into action and put the exterior metal sheathing on the entire house (except the porch) and installed the tubular skylight  in the main bathroom.

Detail number seven: With the weather still cooperating, Phillip and Paul had the perfect window to put our six solar panels on the roof and complete the entire heating system.

Detail number eight: Scott and I drove to Torrey last Friday, met will Phillip to gather signatures, and we took photos of the entire heating system in order to provide the required documentation for our Utah Renewable Energy Rebate...due on March 7.

Detail number nine: Scott spent two days preparing the final paperwork for the rebate and put the whole affair in the mail this morning.

Why a milestone? We’ve made the deadline with time to spare. But even more importantly, Scott is scheduled for back surgery on February 28. We’ll take a hiatus until he’s back in building shape, and we have no looming deadlines to meet. Whew!

Phillip and Paul working on the copper heat exchangers.

Scott down the access hole to the control "room" of our water tank.

Scott receiving instruction from Phillip.

Six solar panels on the roof.

 Scott stroking the panels.

Scott, Phillip and the panels.










Insulated pipes bring water from the panels to the tank and back.

Phillip teaching Scott how the system is regulated from the mechanical closet.

The panels at work bringing the water up to a perfect 140 degrees.

More on Windows and a Bit on DIY

Since we are trying to save money by doing as much of our own construction as possible, it means we absolutely must pay attention to details. Yes, we have subcontracted out many things: cement work, plumbing, electrical and much of the roof. But I guess we are considered our own general contractors because many of the big decisions and much of the precision are, generally, left to us.  Making these choices and ordering the correct items in terms of type and size requires a great deal of research, and this is one of Scott’s fortes. Our windows are a prime example.

As mentioned earlier, our plans called for Loewen Windows, but Scott’s research convinced us to purchase Serious Windows. When ordering windows, three factors come into play: U-factor, Solar Heat Gain Coefficient (SHGC) and Visible Transmittance (VT).

According to The Efficient Windows Collaborative, U-Factor is the rate of heat loss of a window. The lower the U-factor, the greater a window's resistance to heat flow, hence, a better insulating property. (This is similar to the R-Value in walls and roofs.) High-performance windows have a U-Factor of .30 or lower. All of our windows with the exception of the three pictures windows on the south side of the house have a U-Factor of .18. The pictures windows have a U-Factor of .23.

The Solar Heat Gain Coefficient or SHGC is the amount of solar radiation that passes through the window and heats the house. SHGC is indicated with a number between 0 and 1. The lower a window's SHGC, the less heat is admitted into the house. Except for the picture windows, all of our windows have a SHGC of .21. On the south side of the main living space of our house, the eaves will prevent sunlight from shining directly into the house in the summer. However, they are designed to allow sunlight to enter the house in the winter in order to heat the house. Therefore, the SHGC of the picture windows is higher —.50. This higher SHGC also means that heat will escape at night. To prevent this from happening, we'll use insulating curtains on these windows in the winter.

Visible Transmittance (VT) is the amount of visible light that comes through a window. Most VT values are between .30 and .70. Higher VT values maximize daylight and view. The VT on all windows except the picture windows is .4. Since our view is to the south, the picture windows have a VT of .64. More light to see our world.

Just like good glass, it’s amazing what a lot of research will reveal.