Sizing a Batch Rocket Heater w/ Q = G*V*DT and R(or U-Value)

[timeastman]

This was deleted on another folder and re-posted here..

Going through the Reference area and the "Heating" area here and not seeing something that may be obvious but just not getting it. I found Yasin's spreadsheet www.batchrocket.eu/images/rockets/files/Batchrocket_mass_heater_sizing.xlsx but having a question on how to translate westernized R-value (or U-value) to the "classical values" of his batch rocket calculations.

A local company makes SIPS panels so it's likely my house walls would be either 6 5/8" SIPS panel or a 8 3/8" panel (R23 and R29 respectively). Roof SIPS will be 12 3/8" or R45-50 (depending on who's charts you look at).

The question really is this; when going through Yasin's formula Q = G*V*DT with Q being the heat losses (W), G being the insulation factor, V the volume of the house (m3), and DT the required difference of temperature between the exterior and the interior (°C) Is there a factor or conversion to translate R-values to his "classical values"? (listed below)

- 1.8 for an old, leaky, stone and clay mortar house (classical french farmhouses)
- 1.6 for a house in bricks, stones or breeze blocks without insulation
- 1.4 for a house insulated with 4 cm of polystyrene
- 1.2 for a house insulated with 10 cm of polystyrene
- 0.8 for a recent house with 37 cm thick insulating clay bricks for example
- 0.5 for a strawbale house for example


If I just missed it somewhere on the forums here can someone point the new guy to that thread?
Thanks!

[Dan (Upstate NY, USA)]

R value is one thing, you can have walls with an R-value of R40 and R60 roof, but if it leaks air those extreme insulating values mean nothing.

I have a very tight house (tested by New York State taxpayer's money) with all but one wall at R40 and the whole roof at R60.

As I have upgraded the house over the years I noticed the law of diminishing returns when it came to R value. When making the house more air tight had a much larger effect on wood usage.

When I had the house tested I was told to not make it anymore air tight or it would become unhealthy. So I made an heat exchanger that used stove exhaust air to preheat incoming air and closed some other gaps in the house.

Sometimes this is too little fresh air makeup since if I turn on the cooking stove exhaust fan, with the dryer running it can suck the rocket mass heater backwards when its not running...!

[Dan (Upstate NY, USA)]

And I used an 8 inch system. I could have gotten away with a 6" system. I would have had to fire it more often though.