CHOOSING BETWEEN AN 80% OR HIGH EFFICIENCY FURNACE

As this is a DIY Blog, and I get all the questions that come my way. Today I am going to address a question that is coming up a lot

If I am going to do my own Furnace Installation, should I choose a high or mid efficiency furnace? The choice is not so clear so here are some tips to make the choice easier.

The difference in a high efficiency and mid efficiency furnace installation can be considerable if the equipment is installed correctly. For a high efficiency furnace to work correctly it will have to be installed with two pvc pipes going outside. One to carry the product of burning gas out of your home. The other pipe is to bring in fresh air for the furnace to use for combustion.

Now this perplexes some. Why bring in fresh air to burn? Is there not plenty around the house that you do not have to bring in freezing cold air, I dont see how this helps. Thats a great question all. Heres why. When the furnace is burning air naturally from your home it is creating a negative pressure in your home, and all the while the atmosphere pressure on the outside of the house is pushing in with 14.7 lbs of pressure. This causes cold air to find every small opening in your home (like electric outlets, cracks in windows, small cracks from doors) and push that freezing cold air into your home making it very inefficient.

Now if we bring in a little bit of fresh air and pipe it right into the burner chamber on the furnace we increase the efficiency buy not circumventing those natural forces. In fact in theory, and there are some furnaces out there that do this, in theory if you could pressurize your home to 14.8 lbs pressure or close to it, you could possible heat the house with a candle or two as there would be no cold air infiltration.

I know thats a long story just to say, make sure you install the intake pipe………

The efficiencies work like this – if my furnace is 80% efficient, for every dollar I send to the heating company 80 cents would have been to heat my home, the other 20% went into inefficiencies . So a 95% Furnace is a booya no.

Now on to choosing. If I were short on money and I already had a 80% efficient furnace I would more then likely go for another. They are cheaper up front and there is no real added expense to install other then the furnace itself.

When you choose to install a 95% furnace and you have a 80% already in your home , the furnace will not only cost more you should take the following into consideration.

  • The initial cost is more for a 95% furnace, but you could make that up in a few year with efficiency.
  • You will have to install new pipes to the outside of your home – two to be exact, this is extra cost
  • If your hot water tank is left alone piped into the chimney (called orphaned) It will need to have a chimney liner installed so the flue gases can get out of the home and not fall back down the chimney and eat at your chimney. These can be a considerable cost depending on the access to your chimney and the style (but thats for another article)

That should cover most of the needed data to answer the question– New Furnace Installation 95% or 80% ?

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