Is a one story home typically more energy efficient than a two story?

Question

Interested in homes built in late 1990s to present. I have always noticed how the upstairs in a two story home is always significantly warmer that the downstairs. This does not appear to be efficient.

Answer 1

I live in south Texas and have been concerned, but I've never seen a general rule about whether one or two stories are 'better'. What you are describing is more of a problem with HVAC installation or ceiling insulation. I am not an engineer or even an air conditioner salesman though. I think it's fair to say that the top story is harder to heat and cool. In a one story house everything is less effficent and the a/c works harder. In a two story house, at least half is efficient because the lower story has a heated and cooled buffer story against the sun and wind. The south or west side of the house has this problem too unless the a/c contractor is competent enough to compensate.

Look, a cave is generally 65-70 degrees. To me, that's efficient. Because you don't need to heat or cool it. The reason is that the cave has many feet of insulation against the sun or cold. The point is minimize exposure to the elements. So, concentrate on other factors like location, size and price and insulate the roof if you like the house.

Installing seperate systems for upstairs and downstairs lets you cool the downstairs living area in the day and the upstairs bedrooms at night when the sun is not beating down on them. This is more comfortable and saves energy and money, too.

Take advantage of your electric company's conservation program and any tax credits. In the house I bought, the attic vents and fan needed repair. Attics almost never have the EPA recomended amount of insulation. Sometimes the upstairs a/c is leaking air you paid to cool into the hot attic and needs repair. This is especially true in 10-20 year old houses because contractors use cheap plastic ducts knowing they save up front costs and will last long enough for the first owner. However, the lower price is not worth it after a few years because they crumble from heat and age and they leak cool air into the attic so the a/c has to run longer to get enough cool air into the living area.

A later owner then fixes them with higher quality plastic or metal better insulated ducts that last . It usually pays for itself in a very few years.

A ten to twenty year old house is a prime candidate for an a/c system repair/ upgrade. Ask the bank to borrow some extra money for unanticipated costs when you buy it and you can deduct the interest on your taxes.

Answer 2

True, heat rises. Most homes do not have insulation between the first and second floor. Builders try to keep costs down during construction. This is why most tubs do not have shut-off valves like the rest of the house fixtures. A little more thought and engineering could change this.

Answer 3

The problem I see with turning off the downstairs system is the upstairs system will be carrying the load by itself. Unless the downstairs (1st and 2nd floors) and the upstairs (3rd and 4th floors) can be isolated by closing off the areas from each other, you're basically trying to defy the laws of thermodynamics. Ideally, you would want both systems set to the same temperatures and have both thermostats programmed the same.

Answer 4

In theory you are correct. That's why it's now "greener" to install seperate heat/air con for each floor and actually each room should have it's own system. RIELLO SpA of Italy is a great company for this innovative technology.

Answer 5

Depends on quality of insulation and circulation ability of the furnace