Heating Help

Radiator enclosures

After reading the Radiator Enclosures article in the Library here, I'm interested in constructing a few enclosures for our 1-pipe steam radiators to increase their efficiency.  In the first example,marked "Deduct 10%", the article is unclear on a couple of points and I'm hoping someone here can  answer a few questions: 
   
1. What is the "B" dimension for a 36-39" tall radiator?
2. How far above the top of the radiator should the board extend? 
3. Is the board supposed to enclose the radiator on the sides as well as across the front?
4. Will it help, hurt, or make no difference if I put reflective foil behind the radiator?

If someone has built covers in this style, I'd love to see some photos.

Thanks,
Mark

Efficiency means ?

You say you want to add enclosures to increase the efficiency.  Are you expecting to get more heat out of the radiator with the same amount of fuel?  It won't happen.
When people refer to the efficiency of a radiator, they are referring to how much heat it can give off per sq ft of surface area.  Obvious examples of conditions that can affect this are putting a blanket over the radiator.  It will greatly reduce the amount of heat that the radiator can put out.  It will also reduce the amount of steam that the radiator condenses back to water.  So on an output / surface area, the efficiency will be reduced.  On an output / unit of fuel burned perspective, nothing will change. If you set a small fan in front of a radiator and direct the air flow to the radiator, it will greatly increase the output.  It will also increase the amount of steam condensed, and the amount of fuel burned to heat that radiator.   
Adding an enclosure that increases the heat output, does precisely that, and that alone, in the same manner that having a fan blowing at a radiator can increase its output.  While increasing the heat output, the radiator will also condense more steam and the boiler will burn more fuel.  So, if you have a space that is too cool and want to increase the output of the existing radiator instead of installing a larger one, this is a good way to go.  If you have the idea that it is going to save you money on your fuel bill, it won't.

In answer of your questions, you have to measure the the radiator from front to back.  Take this number, add 2" space to the back and 2" space to the front, the sum is the A dimension in the diagram.  The B dimension is 80% of the A dimension.  It appears that the enclosure extends 4-6" above the top of the radiator.  It does not say, and therefore, I assume it is not critical, as long as it is in the ballpark.