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. 

Preping for for solar hot water

There is now a second pipe through the left-side roof close to the ridge allowing for the solar lines to connect to the panel which will be mounted on the other side of the roof (the sunny side)

Looking up through the pipe

The flexible lines in place before we put the pipe through

Its come a little late in the process but we have determined that we can and will be installing a solar hot water panel on the roof.

In order to be prepared for this we needed to put another hole through the roof to allow passage of the supply and return copper lines to go from inside the house out to the panel mounted on the roof.

The lines pass down from the roof through the walls of the 2nd and 1st walls to the basement where we'll eventually connect them to a hot water storage tank.

Pre-insulation and other news

Stops in the rafter bays. These are meant to create smaller compartments into which we'll be blowing in the cellulose. The smaller spaces help to avoid settling in a really long uninterrupted bay

Joe installing the fabric stops

Expanding foam installed between the window frame and the framing

Checking to see what sun is available when. The solar hot water panel will be placed at the upper right hand corner of the roof on the right. The key hours for solar activity are between 10:00 and 2:00. We'll be in good shape with this location

Like the first few raindrops before a shower, there is tangible evidence of our being very close to insulating. I've been spending time installing insulating foam around the windows, Joe has been installing fabric stops in the roof framing cavities, I have the cellulose blower on site, and our supplier is due to deliver 450 bales of cellulose on Thursday. Yes, 450.

We are busily checking off the last few items that need to be taken care of before we start sheathing the walls with Insulweb fabric, which is the first step in the insulating process. Its felt like we've been so close to ready for a while but there are seemingly always a few more things needing to be cleared up.

In other news, we have done some research and have now worked out the arrangements such that we'll be able to install a hot-water solar panel on the roof. This will supply hot water to our boiler so that it does not need to heat the otherwise cold water all the way from cold up to hot. With the collector in place there may be times when the boiler does not need to heat the water at all.

We are really excited about this development, thinking it would be something we'd plan for in the future but couldn't do now. Knowing we wanted to do it eventually, I installed the necessary copper lines so we wouldn't have to open up the walls later on. As I was doing this work it seemed like maybe we should just see what it would take to do it now, knowing it would save some headaches later on. One thing led to another and with the Federal credit it looks like its going to work out.