flexable heating duct

I have a family room built on a slab. The 8" metal duct from the basement is the farthest from the furnace. Air flow and temp. are low. A duct booster fan helped with flow but not temp. obviously. Can I run an insulated 6" duct through the 8" concrete duct and insulate the rest of the metal duct in the basement? Or would that increase temp. and reduce flow? The concrete duct runs about 12ft. to the first register and about 15ft. to the second.
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ok ok ok not good no no and yes ok, ok
Do this... Do a complete set of Manual J and Manual D calculations, then use your flow hood to verify the airflow returning to the furnace, and the airflow coming from each vent. The resulting measurements should be reasonably close to the calculations. If the're not, then you need to re-design the ductwork accordingly then re-test after the work is completed. When your done, if everything is right with the world, the furnace will be quiet, you shouldn't hear any air noise...or very little, and there should be no more than a degree and a half or so temp difference between any 2 rooms. If you don't understand what I have written, then you either need to go back to school, or pay somebody that actually knows what they are doing.
--

Steve @ Noon-Air Heating & A/C

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Let's step back a second - why is the air cold? Well the cold concrete is sucking the heat from the air.
Why is the concrete cold? Lack of perimeter insulation around the slab.
Check around the exterior of the slab for insulation board. If it is not there, you need to dig a 2 ft. deep trench around the slab and put 2" thick blue board around the slab. Make sure you clean off the concrete before applying adhesive to the concrete (you will want to glue the board on to prevent air gaps between the insulation and the foundation - this could create a convective heat loss when you are trying to prevent a conductive heat loss). Make sure you compact the soil when you back fill.
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Douglas S wrote:

Actually;
Find a competent energy audit company in your county and have them do a thermal image of the slab. You'll find that likely there's either no edge insulation or at the very least you'll find heat leakage. The energy audit will at it's very least give you suggestions on how to tighten up your home and / or improve your HVAC as well as the pay-back timeline.
If you aren't really ready to inve$t any money here, then your family's comfort is not that important to you. If you don't like the answer to your question, I'm sorry....
--
Zyp



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ftwhd wrote:

Yes;
They are expensive. So is training. So is the vehicle's, tools, and all that crap. Thermal imaging camera's start around $4995.00 and go up depending on resolution. Air hoods start at $1999.00 and go up from there. Duct blaster equipment starts around $2050.00 for the package and goes up from there. Blower Door Systems start at $2525.00 and go up from there. What's your point? Either you are an energy audit professional, or you are not. Either you want an answer to your problem [meaning the original poster] and the solution or you don't. To generally get an answer, at least from my company, it starts at $550.00 and goes up from there. That'll get you about 3 - 4 hours of inspection work and an Energy Pro audit.
--
Zyp



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ftwhd posted for all of us...

The fire co? Mine does. yes $$$$ big bux. But don't call for your heating system for this purpose, remember we also have axes... and know how to break things.
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Tekkie Don\'t bother to thank me, I do this as a public service.

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I do this type of diagnosis/consulting with an IR imager on a regular basis for $350 and there are a few others in my area who are about the same price. If we don't have to write up a full report and you're just looking for a problem-solving consultation, we keep the rates in that range. If you need a comprehensive report on the whole house, then yes, $550+ is the norm.
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It's spelled 'flexible'. Spelling counts!
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Who gives a rats ass if its not gonna effect your base rate of pay.

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I guess you've never raised kids..........
If you did, they're stupid.
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Actually I have raised 2 of them... both with full ride scholarships, one earned her education degree, Summa Cum Laude and is finishing her Masters, the other is on the deans list in her second year. BTW... I am retired military, hold a Masters in Mechanical Engineering, and am a certified Master HVAC tech, as well as having been a business owner for the last 12 years.
Would you care to try again??
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