Rumours, Remakes & Radiant

Sometimes cover versions of hits only make you miss the original.  Not this one…

Graham Parker and The Rumour put a hurtin’ on the old Jackson 5 hit in 1979. Graham Parker, of course, was born in 1950 – the same year as DIY author Hubbard Cobb published his homage to overestimating your skill set, Your Dream Home: How To Build It For Less Than $3,500.

The 1950 DIY dream home was equipped with radiant floor heating, in this case copper tubing in the slab.

Cobb provides a fairly broad set of instructions for the tubing installation, ranging from the silly (install the tubing before you pour the slab – duh!) to the serious (don’t let the tubing come in contact with cinders, which cause corrosion).

Slab insulation was only hinted at back then.  Cobb says only to make sure the edge of the slab-on-grade structure is insulted – vertical insulation extending down at least 3 feet instead of the then-standard 18 inches.  We now that while you can “get away” without insulating under a slab  (only if there are no water table or rock issues), it’s way better to insulate under the entire thing.  It cuts down on the load and makes the slab a tad more responsive.

There’s no discussion of finished floor material, nor its affect in radiant system performance.

And speaking of the load, the author recommends a boiler with rating of 96,000 BTUH.  The walls are 2×4, with 3” of “blanket” type insulation with a vapor barrier, and the overall sized of the space is roughly 1,300 square feet.

A little research shows that a circa-1950 boiler may be, at best, about 75% efficient, giving us a usable net output of about 72,000 BTUH.  A little math says that 72,000 BTUH divided by 1,300 square feet would equal just over 55 BTUH per square foot.

To deliver that kind of heat, the floor surface temperatures would have to be around 97 degrees.  Ouch!

Then, as now, it would be important to “do the math!”

Now take a good look at the boiler piping schematic:

Note the “stop & waste” valves on the return lines from the radiant system.

“The purpose of these valves,” writes Cobb, “is to allow you to control the flow of hot water through the various rooms and so get varying temperatures according to your own taste.

“If you wish to keep the bedrooms a few degrees cooler than the living room, the stop valves at the end are partially closed off.  This reduces the flow of water through these panels without any effect on the flow of water to the other panels. “

Well, yes and no.

Yes, partially closing a stop and waste valve (known in heating circles as a “globe” valve) will reduce flow through that particular loop.  There will, however, be a slight increase in the other loops due to the phenomenon known as “dynamic” balancing.  In a closed loop system such as this one, with a circulator making the water go round and round, it’s impossible to adjust flow through one of the loops without affecting the others.

A change here equals a change there.  It’s sort of like making a balloon animal – when you twist and squeeze one end of the balloon, the other end feels it as well.

Now, in a big old concrete slab like that, I’m not sure how much “tweaking” the flow will make a difference.

There’s lots more to share in this fascinating book.  We’ll do that next time!

Also born in 1950, one of the greatest drummers of our time, Carl Palmer of Emerson, Lake and Palmer.  Check out the drum solo starting at the 2:44 mark…

Now that’s impressive!

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