Stubby wrote:
...
The furnace and water heater are in a utility room that draws air
through vents in the door which opens to the outside.

Therefore the utility room is outside of the house. Walls
and door separating utility room from rest of house must be
insulated. Pipes into and out of heater and hot water must be
insulated. Insulation around the water heater should be
supplemented since water heaters are normally insulated
assuming room temperature environments. Meanwhile, what is
the vintage of that furnace - a question about its efficiency?

Appreciate the concept. The house must be completely
encased in same insulation. Any hole in that insulation
negates most all adjacent insulation - which is why so many
homes have energy loss where interior walls join to outside
walls.

You cannot correct the slab. You cannot dig beneath and
maintain a stable house. Homes on slabs (especially with heat
in the slab) were a bad idea - from an energy perspective.
You could dig outside the foundation up to 3 feet down to
place insulation. Then cold does not go under wooden walls to
cool the floor.

Appreciate how badly Americans built homes even in the
1970s. Ironic, that a gallon of gas in 1969 (at 2005 prices)
was $1.80. Recently people complained when gas went from a
ridiculously low $0.85 to a just as low $1.20. Energy was so
cheap in 1970s that we only insulated walls in more expensive
buildings. We put a hottest part of house - hot air ducts -
almost directly in contact with outside cold - and called that
high quality construction practices. It suggests how much
wealthier Americans were back then - or how much intelligence
has finally been grudgingly forced upon an American public.

Why are you really concerned about the price of energy?
Because in the 1970s, a gallon of regular gas went from $1.80
to well over $5 per gallon - in 2005 dollars. Good reason to
expect history to repeat itself now that less energy is
discovered every year compared with what is consumed - meaning
we have a severe innovation problem. All factors that
contributed to an economically depressed 1970s - including a
lying president, inflation, excessive federal government
spending, an unjustified war, and increasing energy prices -
also characterized the 70s.

History demonstrates that people do not take energy
consumption seriously until gallon goes to maybe $7 per gallon
- 2005 dollars. IOW you would be simply getting ready earlier
when doing so costs so much less.

No way around an energy inefficient design - a slab. The
damage has been done. You must minimize the damage.

The good news - many options exist to improve energy
consumption.