We started drilling the ground source heat pump wells last week. We’ve had a couple bumps which I thought I’d share about.

But first maybe I should give a little explanation of what I’m actually talking about.

Ground source heat pumps in homes are used for heating both hot water and the home interior. Generally, they are a water based system – they heat water, rather than air, like your typical forced air furnace.

Ground source heat pumps essentially combine two very efficient technologies to result in an extremely efficient technology. They include two parts: a ground well system for preheating the fluid to the average ground temperature (in Issaquah, 50 degrees or so). Once the fluid has run through the ground well field and been prewarmed, it is then run through the heat pump, which then heats it further up to 125 degrees or thereabouts.

The radical thing about using the preheating loop is that effectively, the heat pump only has to heat from the 50 degree baseline, year round. That means that in the dead of winter, when it’s 30 degrees outside, the heating system is effectively only having to heat from 50 degrees, since it’s using the well field water. The heat pump has its own cool efficiency which I’ll explain another time.

So, back to our well field. To create our well field, our mechanical engineer (Stantec in Seattle) determined the appropriate sizing based on the total heating load for our ten units. They determined we needed 3,000 feet of vertical wells. Our initial design configured that 3,000 feet into ten 300 foot deep wells connected by a set of pipes (called a manifold) just under the surface.

Into each well, a very heavy duty double U shaped one inch diameter pipe is run down the bore hole. The pipe is made out of polyethylene, and is the same pipe used to carry natural gas to homes. The pipe is then grouted in place with a material called bentonite, which is a sort of flexible inert concrete. The grouting ensures that the pipe and the fluid inside the pipe is in full contact with the surrounding ground, to maximize the thermal conductivity.

The problem we’ve run into is that we’ve had some issues boring holes that deep. Portions of Issaquah Highlands are an old lateral moraine from the big Puget Sound glaciations of the last Ice Age. There are lenses of gravel which tend to collapse when we’ve drilled through them. In particular, there is a lens at around 200 feet.  As a result, we’ve had to modify our well field, and increase the number of wells to fifteen or thereabouts. It’s added cost and taken more time.

I was in the field yesterday watching them place one of the pipes and grout it in place. It is tough work for the drillers – sledgehammers, rubber boots, hard hats, a big drill rig and a lot of sweat. It was a very good reminder to me that this is where the rubber hits the road. After years of planning, evaluating the options, and weighing the pro’s and con’s, here was a crew of three guys working hard all day, drilling a hole, muscling a tube down the hole, mixing a big batch of grout, pumping it down the hole, and moving on to the next one. When zHome is done it will be a mix of brains and guts and stamina.

Details of time and location have not yet been finalized, but zHome will be participating in this conference at Evergreen College.  Check this interesting conference and come see us in action!

Issaquah Press article 

Issaquah Reporter article

zHome starts construction tomorrow, April 6th!  After some initial utility work, we will be installing the ground source wells.  I will do a separate post on that, and include some video so you can see what it’s all about.  We will also have an onsite informal get together next week if folks want to view the well drilling.  We will be continuing construction for about a year, when we will open for public tours.

So, how did this come about?  Howland Homes, our builder partner, has formed a joint venture with Ichijo USA, which is providing project financing.  Ichijo USA is the American subsidiary to the Ichijo Group of Japan, which is a major homebuilder there.  Last year they built about 8,000 homes with a total sales value of $2.1 billion. Ichijo is currently building highly energy-efficient homes in Japan, including the i-cube, which includes a heavily-insulated exterior (R-30 walls) and air source heat pumps as standard specification.  They completely get what zHome is about, and have been real leaders and innovators in their home market. 

It feels great to be starting construction.  The team is really excited to begin our education program and start rolling with our market transformation.  I am personally incredibly excited to have Ichijo as part of the project.  zHome is now international in scope, influencing not only Issaquah, the Puget Sound region, and the Northwest, but potentially Japan as well.  If we are going to be serious about addressing climate change, it is going to be these sorts of international partnerships that are going to do it.

More on details of all this as we move forward – I just wanted to get the word out!