What to do first in a house with poor thermal performance and high energy bills

Question

I just moved into a house and am a little bit disappointed in its thermal performance so far. It's winter and cold outside, and the furnace heats the house up pretty quickly, but then the house gets cold again pretty soon. So the furnace is on, then off again, then on again, and I suspect it's not reaching its efficiency potential from this. Furthermore, the dry air blown around the house isn't terribly comfortable in the already-dry northern New Mexico climate. The tile floors set right on top of the slab are really cold. The gas bill is irritatingly high.

So I'm wondering what I should tackle first to to remedy this situation. Here are some more details:

• The house is a 42 year old ranch-style, and the conditioned space is 1,200 square feet.
• The house faces west, so the main living area only gets direct sunlight early in the morning and in the late afternoon.
• The heater is an 80% efficiency 125,00 BTU central forced air furnace with ducts in the unconditioned attic and vents in the ceilings.
• There are lots of air leaks.
• There is a large sliding glass door that was double-paned, but one pane is missing
• The entry door is un-insulated.
• The walls are 2x4 construction with fiberglass insulation.
• External sheathing is cream-colored stucco, with no continuous foam insulation or anything nice like that.
• The attic has loose cellulose insulation, about 6" maybe. Higher in some places, lower in others.
• The roof sheathing is made up of light red asphalt shingles. Roof decking is 2x10s.
• The house is built on a slab-on-grade which is not insulated at all. The footings have been extended outwards to form a ring of concrete around the whole house that you can walk on, making it impossible to effectively insulate the edges without removing the extra concrete first.
• The windows are double-pane, but old and aluminum-framed. The aluminum frames feel very cold to the touch when it's cold outside. They also do a terrible job of noise cancellation. Inside the house, you can hear people 30 feet away outside.
• There is an attached, uninsulated garage.

What should I do first? I'm planning to stay in this house a while so I'll have time to tackle large projects eventually (i.e. replace shingles with metal roof, add continuous foam insulation) but I'd like to know what's the general order I should tackle things.

Answer 1

Stop the leaks

You're paying good money to heat/cool the air, keep it in your house. Check the exterior for obvious leaks such as air blowing through a door gap or windows that don't close all the way. The less you absolutely need to use that area the easier the solution is. If it is a hole in the wall fill it with some insulation batting, if the window is cockeyed and not sealing cover the gap then seal the window with shrink film for a temporary solution while you're getting the rest of the house under control.

After you have the air contained make sure its going to the right places. Check as much duct work as you're able to get to for leaks, small gaps in joints or corners can leak air that will short cut the system and waste your money. Aluminum tape is recommended here but just simple duct tape would work as well. Might not hurt to throw out the money to have a furnace guy come out to check over the system and make sure the controls are all working properly and you're getting as much air through the vents as you're supposed to.

Insulate

Go through and prioritize what you can afford now and what you need to put off and how much they will effect your heat loss. Your priority #1 better be that sliding glass door, They have a very large surface area with less insulation than walls (in most cases, tbd in yours) and with one pane of a double pane broken its lost a tremendous amount of its insulating factor.

If you do not want to insulate the bottom of your roof in the attic then by all means wrap insulation around all the duct work which is in the attic, I would recommend both. Adding additional cellulose insulation to the attic would not hurt but will likely have less of a benefit as most of the other things listed.

Replacement windows will help but there are uglier things which can be done in the mean time which are much cheaper that could help get the costs and comfort under control such as storm windows.