Technically, today I managed to make the Bunkhouse meet the Heating Load requirement for Space Heating (and I almost met the Annual Heating Demand requirement as well!) I say technically because it was never the plan to spend $100k to build a $10k trailer. However, since it was all on paper, I decided to see what it would take. The Annual Heating Demand and Monthly Method worksheets gave me some visual feedback to help me decide what needed tweaking to get to my goal.
Let’s start by understanding what the Annual Heating Demand and Monthly Method worksheets are for. These worksheets are both designed to meet the EN 13790 method of calculating the heating demand for your project. The PHPP manual states that both methods give similar results with the Monthly method being more accurate, but the Annual method easier to understand. I found I used the information on both worksheets to help me understand the project. Only one can be chosen as the basis of the heating demand calculation for the PHPP (and this is done on the Verification worksheet), but you can still look at the graphs on both the Annual Heating Demand and Monthly method worksheets to help you understand what is going on.
Here are the charts I ended up with after I threw lots of money at the project and met the Heating Load requirement:
You will see that the Annual Heating Demand chart shows where I can expect to see the heating gains and losses and at what percent. This helped me decide between more insulation and changing window sizes. The Monthly Method chart showed me how much free heat I could expect each month and also showed me when I could expect overheating. The Blue line on that worksheet shows me what my losses are for each month, but not where specifically I am losing the most heat. That’s why I used both charts. By looking at both charts I could see how changing the window sizes would affect both overheating and heating. I could see how adding insulation affected the heating demand on both charts as well, but the Annual Heating demand sheet broke down the difference between the losses from the walls and those from the ceiling/floor areas so I was able to target where the additional insulation would do the most good.
Because the PHPP mentions that the Monthly Method was harder to understand I decided to see if changing the chart slightly would help me see it better and I found that I like it this way. (I didn't change it in the PHPP, I just made one by hand). I put the Solar and Internal Heat Gains on the bottom of the chart (in yellow) since I knew I automatically had those. Then I placed the Heat Demand (in red) above those to show what I would need to make up for the additional losses that I could expect (the blue line). I also added an area that shows overheating more clearly for the summer months (yellow with red cross hatch). June and September are actually special cases with free heat, heat needed, and over heating all in the same month. By color coding these charts and studying them you can really get an understanding of your project.
So, technically I was able to get past the first hurdle and meet the Heating Load requirement on paper. But what does the Bunkhouse look like overall and close up? Up next I will draw the bunkhouse to scale with the window sizes that worked and see if I can find out exactly how many gold bricks I would need for the vacuum panel insulation. I’ll also pull together some PH nerd numbers for all the folks who are wondering about R values and TFA.
Up Next – Bunkhouse Nerd Numbers.