Tell us about your typical weather/temps for your location, both winter and summer.

Can't believe you need an 80 KBTU furnace and don't care at all for the idea of mixing brands. In fact, I would go farther and say it is irresponsible.

As far as Clean Effects, you need to have a clear understanding of a homeowner's responsibility for regular cleaning/maintenance that this air
cleaner demands. If you are not willing to take on this issue, then I would stay away from it. Personally, I would not have one and would opt for a good pleated filter media cabinet like the Perfect Fit that matches to the furnace.

I would like to see in writing the city code that demands a 64 db rating. I can only think of several that would be meet that standard. My Trane condenser is rated at 74 db and I can not hear it inside and have to be close outside to hear it. In fact, I hear my neighbors which is louder than mine.

IMO

tigerdunes - thanks for your reply. Not sure I understand your comment about mixing brands. Are you saying we should have the same brand AC as furnace?

As for the 80K furnace, yes, it does seem like overkill, but our energy calculations show that the new space alone required just under 40K for 1000sqft. Now adding 550sqft the requirement would likely go up to 60K or slightly higher given the orientation of the house. The new part is Southern facing and has been designed to take advantage of solar heat gain. The old part is North and the shadiest and coldest part of the house. I think the logic from the HVAC person was that we could go for a 60K system but the incremental cost is $150 so size up. Not sure that is valid logic but I'm guessing that's the reasoning.

As for the db ratings, yes, I have a copy of the city code requirements and it is true. This low requirement is based on the location of the unit. We have to put it on the side yard because we are at setback in the back. Side yard placement has stringent noise requirements. Alternatively, we could place the unit in front of the house but it would be aesthetically unappealing.

Thoughts?

Thank you!

You did not provide typical weather/temps for summer and winter. Pls post.

I would go no higher than a 60 KBTU furance at 95% efficiency.

And yes I would stick with one brand both furnace and AC.

For as little as you will use the AC, a good basic 13 SEER condenser
would be fine. However it will be problematic to find one with a low Db rating.

I personally would contact your City Manager and see what procedure if any is available to get a variance on such a stupid and restrictive code.

I do know Lennox makes a low Db rated AC condenser but it would be expensive.

IMO

The winter temps will go down to mid 30's at night but up to low 50's during the day. During the summer, mornings are always cool in the 60's and for 1-3 weeks a year we will hit the high 80's. Else it will be in the mid-high 70's.

"...there are times when we would use the system at the 2nd stage for air cleaning - essentially running the unit to clean the air during high allergy season."

Has anyone seen any data that indicates doing this helps with allergies? With forced air ducts on the outside of the living space, I'd be more concerned with keeping positive pressure inside the house with filtered, controlled venting if outdoor allergens are involved. "Seasonal" indicates outdoor, but problems during construction might not. If you need to control allergies, the first step is figuring out what that person is allergic to.

Allergies are both seasonal and dust/mold related. But your point is well taken. Need to know exactly what I have to combat. Thanks.

Doing a follow up post as we need to make our choice in the next week. We are going to scrap the AC. Have lived in the house for 18 years without it so we will be fine especially since we are upgrading insulation, putting in new windows, etc. Further refinement of the heating loss/requirement calculated as part of our CA Title 24 req's yields a need of 61,000BTU. So the question goes back to sizing of the furnace.
Here are some other (corrected) details:
-high window/wall ratio (in fact there are 2 of three exterior walls in the new space are almost all new windows)
-R38 cathedral ceiling
-R13/19 floors/walls
- day time temps up to 55 nighttime down to 36 (yesterday it got up to 70 during the day!) so sometimes we crank the heat in the morning and then wind up opening the windows in the afternoon.

From the TRANE site:
Model Nominal Capacity Output (BTUH) Stage1/Stage2 AFUE
TDH2B060A9V3VA 37,000/57,000 95
TDH2B080A9V3VA 49,400/76,000 95

So it seems like we are between sizes. It seems typical (I didn't say "right") that people size up (bigger is better).

THoughts??

Thanks

Stick with the 60 KBTU model and look for opportunities to lower your heating load through insulation improvements, etc.

And it's important to get a true two stage thermostat that controls a two stage furnace rather than a timer on the control board. Big deal!

And bigger is not better.

IMO