Numbers

I recently gave a presentation to the Super Insulation class at Yestermorrow Design/Build School about building and living in our house. This presented a convenient opportunity for me to take stock of the building process, consider our experience living in the house so far, and to put together some performance numbers. We've been in the house just under two years and have established a track record for firewood consumption and are starting to get some reliable numbers on our propane and electric costs.

When our home was completed Efficiency Vermont (the state energy conservation organization) tested and evaluated our house for energy performance and determined a HERS number, which was presented as a part of their evaluation. HERS stands for Home Energy Rating System and is the standard methodology for comparing performance across buildings and regions. Many factors go into the rating system, including air-tightness, window performance, efficiency of the appliances, lighting and heating systems, as well as design specs like insulation R-Values and so on. The rating is adjusted for climatic conditions in a given location.

This is a generic chart showing the HERS rating scale. The "This Home 65" has nothing to do with our home.

In the above chart, 100 equals the energy use of a new home built to conventional standards in 2006. This is used as a base line by which to evaluate the spectrum of performance across buildings.  A rating of zero means the house requires no energy at all, while a rating over 100 means the house is sub-par in relation to current norms.

Our home earned a HERS rating of 38, which is a "5 star +" in the star rating shown below.  The scale somewhat curiously goes from 1-5 stars and then has a + category.  (Maybe they needed to add a new category as more efficient homes are being built -- I don't know.)

The HERS rating laid out estimated energy use predictions for our home as follows (calculated in 2011):  

             26.6 MMBtu heat  $990

             10.1 MMBtu hot water  $375

             17.9 MMBtu lights & appliances  $704

             HERS estimated annual energy cost:   $2,188

Based on our actual usage, these are our costs:

           $100-$150/yr firewood

           $750 propane hot water/cooking

           $768 electric

           Our actual annual energy cost:   $1,668

In the nearly two years we've been living in the house, we have only heated by wood. There is the radiant system in place should we ever choose to use it, but for now we like heating by wood; it's easy and feels good.

Although we know from experience that our heating expenses are tiny, it is useful to see them laid out together with the other home energy requirements. We plumbed the house in preparation for installing a solar hot water system, and seeing these numbers is a good motivator for costing out the completion of that project. It would feel good to bring the hot water energy numbers down. 

Wood Use Check-In

This week we are just finishing up burning a total of 1/2 cord of wood so far this season.

(Since our wood is all cut to 12" long, it is easy to quantify the volume of wood we stack between the posts on the porch. I have a mark at the height of a quarter cord and can easily mark the heights for fractions of that quarter cord.)

Last night Nancy and I discussed how much more we should load onto the porch. I suggested another quarter cord, or maybe an eighth. We settled on a sixteenth.

With the strong sunshine at this time of the year along with warming temps it just doesn't seem like we'll burn too much more wood.

Now that we are beginning to understand our heating requirements the information allows us to consider how we might source our wood needs. In the years we lived in the yurt we needed so much wood (about 3.5 cords per season) that cutting it ourselves was not really a consideration. Harvesting a half cord just doesn't seem so hard so its interesting to think about harvesting our own wood supply from the surrounding woods.

Wood Use

Later on January 14, 2012...our second 1/4 cord stacked

January 14, 2012...the last of our first 1/4 cord

January 1, 2012...roughly an 1/8 cord

September 24, 2011...our first 1/4 cord

Its been fascinating to monitor our wood consumption this fall and winter.

By New Years Day we'd used just over an 1/8th of a cord which you can see in the middle photo above. Now, two weeks later we've used most of what was left. This means it's taken about three and half month's to go through a 1/4 of a cord to heat a 17oo sq. ft house.

Of course it has been a mild fall, so this may not be indicative of future use, but it starts to lay out a pattern for us to plan around. January and February are the coldest months of the year and it will be interesting to see how much wood these months require. It seems like a reasonable guess that we won't go through more than a cord total for the year, but we'll see when all's said and done.

(I've spent some time trying to figure out a way to present energy use in comparable terms and I'm not there yet, but I want to work it out so it can be presented in a way that would allow comparisons with other forms of fuel, house size, and energy efficiency.)

In dollar terms we paid $200/cord in July for the wood we have on hand now. Roughly this translates to about $50 to heat our home so far this heating season.

The quarter cord we are just finishing burning is a couple years old, so its delivering more btus/kwhs then the woodstack we are about to start using which has not had time to fully season. The new wood was (presumably) cut and split in the middle of the summer since we had it delivered at the end of July. After this season it will be easy for us to maintain a seasoned wood supply by having one dry cord to burn and stocking up a green cord each summer.

Chilaxing

Sunday Times by the woodstove after a ski

The gang chilaxing

Our first official meal. Hooray!

This weekend we had the privilege and the pleasure of hosting our first house guests in our "new" house, and it was a terrific experience.

Michael, Anu, and Scott arrived late Saturday morning for a lunch before we all headed out on either a back-country ski or a walk. The weather has been blustery and cold and after a few hours out, coming back from the surrounding hills we found house was as welcoming and warm as we could ever dream. A small fire in the woodstove and warm-up shower thoroughly defrosted as needed.

Anu cooked us an excellent Indian diner and the kitchen served us well. There's still lots of organizing and such to get in place, but the basic experience is solid.

In a really neat twist of fate, Michael and Anu were some of our first guests when we moved into the yurt almost eight years ago. We were glad to have them here again celebrating with us.

This week I'll continue working on the various small projects required polish things off for the final inspection from the appraiser. This includes a shelving unit in the kitchen, some finish work over the stairs, a cap on the railing and some trim work around the t.p. holder/storage cubbies in the bathrooms. Oh yes, also I'll be working on light fixtures.

Site Plan

(Click on the image to embiggen it)

Today (and yesterday) I worked on our site plans. The big bugaboo all along has been what to do with the cars. We hoped that removing the garage would make it a little clearer, but its still a question.

I've been spending time playing with different configurations and today, with Nancy making some key suggestions we think we landed on a reasonable solution. We'll have to shift the little shed a bit, but we should be able to fit the cars next to it and keep them from being the center feature when you either come down the driveway or look out of the house.

We also thought about where we'll store our firewood such that it is accesable and near where a delivery truck can dump it. What is not really solved is where to store bikes so that they are handy, sheltered and otherwise secure. Hmm....