HVAC recommendation for 3rd floor (attic) unit, poorly insulated

4 Replies

I have a heat pump that needs to be replaced.

Residents currently have window AC units, but have complained that it is not cool enough ( rarely falls below 78 degrees on a hot day)

No complaints from residents when heat pump worked. 

Mitsubishi multi zone HP 24,000 BTU + 2 wall units install quote is $7,445.10, approximately $1,000 less for electric baseboard heat install. 

I am getting two other quotes from HVAC companies and have yet to hear back.

Would you do the less expensive electric baseboard heat with separate Central AC unit or go with the Mitsubishi mini-split for AC + heat or would you consider getting a quote for extra insulation (not sure if there is an easy way to blow it in)?

Any advice would be greatly appreciated. 

I would replace the heat pump unit and air handler (potentially adding a heat strip in it). If you already have the ductwork ran etc. a heat pump is the simplest way to heat and cool in a moderate climate in my opinion. If you're in an area that gets below zero a heat pump may not cut it. At which point you may want to add a heat strip in the air handler. If you opt for this just check with an electrician first because a heat strip can draw a lot of power 30 - 50 amps.


Check out this link to an article on Carrier's website.
https://www.carrier.com/residential/en/us/products/heat-pumps/heat-pumps-vs-air-conditioners/

Furthermore if you can find a local HVAC engineer or energy calc specialist to run energy calcs for you they can tell you exactly how many tons of heating and cooling you'll need based on the SF of the house, type of windows, type of construction (wall make up, floor make up, roofing etc.), how much insulation is currently installed etc. You can then have he/she run the calcs and plug in an upgraded type of insulation to say spray foam for example. That should reduce the amount the tons required to heat/cool space therefore reduce the cost of your system.


From my experience spray does a great job but it can be costly. It goes for approximately $2.50 - $3.00 per SF of roof in my area. 

I wouldn't do the electric baseboard heat anywhere it would be needed more than a few weeks a year - so unless the house is in, say, Miami, Houston, Phoenix, etc, then I wouldn't do it.  It's cheap to install but expensive to run.  I know the tenants probably pay the electric bill, not you, but it can become an issue if it makes your unit a lot more expensive to live in than the competition.

Is the broken heat pump central?  If so, why not put in another central heat pump?  (Maybe that's what the other HVAC companies will quote.)

Do you have gas (I beg your pardon)?  If so, it's possible to do a central heat pump with a gas furnace, if you want.  The heat pump provides the heat in the spring and the fall, but when it gets really cold in the winter, the gas furnace automagically fires up.

The HVAC salescritters should know about it, but it's probably worthwhile to check with the local utility companies to see if they have any rebate programs, and what it takes to qualify for them.  Sometimes you can get money for installing a more efficient furnace or A/C; sometimes they will also pay rebates for better insulation, windows, door weatherstrips, etc.  Sometimes, for the furnace and A/C rebates, you need to have a tech test your old system before it's removed (or at least note the model number if it's broken); sometimes you just need to write down the old and new model numbers on a form.

If there are any end walls in the attic, and the outside is vinyl or wood siding, it's possible to remove a strip of the siding near the top, drill holes in the outside wall, blow loose insulation into each stud cavity, plug the holes, and put the siding back.  If the end wall is a small part of the total wall/roof area up there, this may not be worthwhile, but if it's a big end wall it might help a little.

@Matt R. Thank you for great info.

There is no gas line to 3rd floor.

I’m in Ohio so sounds like electric baseboard heat is not best option.

Good point on replacing central heat pump if that is what is in place now. I will touch base with Hvac folks to see if that is feasible and less expensive.