Addition Questions

Old 09-11-02, 11:03 PM
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Question Addition Questions


I'm doing an 800 foot two story addition and to save money I'm planning on doing the heat addition myself.


The house is located in moderate NW (Washington state) so we don't get any large temperate variances (low's in the high 20''s and highs in the 80's). The house is currently 1980 square feet with the upstairs being a large open air loft. We have a lot of glass on the front of the house. The addition will add 2 bedrooms upstairs and a TV room in the back. The house was built in 1991 using 6" (ID) flex ducts for delivery.

My plans:

I'm planning on doing a fairly simple extension of the system, using 6" metal ducts and "T"-ing off the existing registers in four places. I think I can get away with this as the air pressure is very strong, especially downstairs as the furnace is only 5 and 15 feet away from where I'm going to extend it from. The extensions will go about 16 feet into the new addition outer wall.

A couple of questions:
1) Is it crazy to think I can just T off the existing registers?
2) Do I need to insulate the metal ducts (one advantage of the flex ducts is that its insulated)?
3) How likely is it I need to increase my furnace size and can I do it later if I find its under heating the house rather than doing it now?
4) Anything else I should be thinking about?

Old 09-12-02, 07:51 AM
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Hello B. Masters. Welcome to our Heating and Cooling forum and the Do-It-Yourself Web Site.

There is always lots of things to take into consideration when performing a task or project like this. One of them is the ability for the existing heater to heat the additional square footage.

Adding ducting and registers to an existing forced air heater will reduce the overhaul heating ability and capability of the existing force.

If this unit is downstairs, forcing air upstairs could pose yet another problem and prove to be an unexceptable problem after the work is already completed, etc.

Lots of other unforseen conditions and potential problems may exist which cannot be determined here in a text only format. Other unknown conditions could prove that your desire to save some money initially, may not provide the desired end results.

May be a worthy suggestion to recommend you contact several local heating contractors and consider their professional advice. Possibily contacting the local city building depart for additional suggestions and obtain the rules and codes as they pertain to your area.

Still yet, it may be adviseable to consider a seperate unit soely for this area for energy cost savings over the longhaul.

Several other resident heating and cooling professionals on this type of heating system, replying within this forum, could have additional helpful information, suggestions, advice. Check back on your question several times for additional replies.

Read the ARCHIVE postings, within this forum, for additional information on this topic and the replies offered.

If you need further assistance, use the REPLY button to add any additional information or questions, etc. Using this method also moves the topic back up to the top of the list automatically.

Regards & Good Luck, Forum Host & Moderator.
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