Adding cooling to 1990s Montana home
Here is the scenario: My dad just bought a 1990s single family home in Montana, where he has never lived (nor have I). We are now in the process of updating the home, which has hydronic heating embedded into the slab on grade. I know that system may or may not be nearing the end of its life 30 years later, but the intention is to continue using that radiant floor system to heat the home. We now want to add cooling, as summers are getting hotter. The two-story house only has 8′ ceilings, and I am worried that the plenum is not large enough to introduce a ducted system without dropping soffits everywhere (I’d like to avoid this if at all possible).
So, my thinking is to install radiant hydronic cooling in the ceilings, and switch out the boiler for some kind of equipment that can run both hot and cold water (I’m very new to construction so I don’t know all the correct terminology yet. Is this a heat pump? A chiller? Basically a reversible evaporator/compressor that can send hot water to the floor in winter and cold water to the ceiling in summer.) If this is possible, I would also need some way of getting fresh air into the home, possibly using an ERV.
As I’m very new to this, I’m looking to get some expert on opinions on: 1. should we be abandoning the radiant floor heating all together? I believe the pipes are copper. 2. Would the need for an ERV or other fresh air ventilation system give me the same plenum/soffit problems as just ducting the space? Are there ways to bring in fresh air that are less space-intensive? and 3. Are there any other possible solutions for cooling the home that I’m missing?
For reference, I do not want to install mini-splits because I think they are horribly ugly, and my main priority is a high indoor air quality and maintaining the ceiling clear height.
Feel free to explain things like you are speaking to a ten year old, and thanks in advance for the advice!
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Replies
More information is needed here.
Is this a gut rebuild? Are your walls open?
Do you intend to have a conditioned attic?
And yes, systems that can heat and cool typically are ASHP- minisplits. But, the distribution does not need to be via wall hung evaporators. Lots of options here.
Generally, I'd abandon old copper radiant too. Long discussion there, more to the system than just the piping.
Thanks for the reply! It is not a total gut reno, but we are moving some walls around. The current oven/range does not even have a vent hood system installed, so some type of ventilation will need to be added to the home. I'm not sure what the wall section detail looks like at the moment as no one has gotten into them yet.
Could you detail a few of the options for mini-split systems that avoid that large wall unit? I've seen some people box that unit in with a decorative grille, but I've never heard of a mini-split option that does not use that visible fan box at all. Is there a reason you'd choose a VRF over radiant heating/cooling?
I'd also like to hear your thoughts on abandoning the radiant heat in the slab. Ideally I'd like to reduce this home's reliance on gas and move to electric, but my dad thinks even switching to a tankless water heater is not feasible in the Montana climate (he wants a combi-boiler).
Any options you can suggest I look into would be helpful as the project is progressing on a tight timeline and I need to start locking down systems. Thanks again!
Moving walls around creates a high risk of puncturing radiant piping in the slab.. Also, if the piping layout was done with the current wall configuration in mind, then you are likely to have warm/cold spots in the floors of the remo0deled rooms. There may also be chemistry/corrosion issues with in-slab copper pipes. In a 90's house, there may or may not be good underslab and slab-edge insulation, so much of your heat may be escaping in those directions. Simply put, using old radiant systems is risky.
Radiant cooling won't work in most residential settings because you need a dedicated dehumidifier to address water vapor. Otherwise, you will get condensation on the chilled surfaces. Adding a decent dehumidifier will likely require ducts that you are trying to avoid. OTOH, if you are going to the effort of adding radiant cooling to the ceiling (with dehumidification), it can be used for heating, too. Ceiling mounted radiant heating has the advantage of not being covered by carpets, furniture, etc. Air-to-water heat pumps are getting more popular and would be entirely appropriate for this application.
You can also get "ceiling cassettes" for minisplits that would provide both heating and cooling. Relatively low-profile and quiet, these work best in open plan spaces. Bedrooms and other rooms that are frequently closed off are tougher to condition with minisplits.
There are so many options out there that it's tough making specific recommendations. Most of the systems that we discuss on this forum are relatively new and/or cutting-edge. Most HVAC contractors will not be familiar with them and may not have the expertise to adequately design and install a system. If you are thinking about using modern technologies (and minisplits qualify even though they've been in use for 30+ years), you might want to shop for a contractor first and design your system around their expertise and local knowledge.
Though I hate to even bring it up, the most common approach with a house like yours is to insulate the roof, making the attic a semi-conditioned space. Then, install a traditional forced air HVAC system for heating and cooling with ductwork in the attic. There are lots of reasons why this approach is problematic, but if the system is sized right and ductwork designed properly, this can be effective and efficient. YMMV.
Peter beat me to it!
There are short run ducted units and floor mount units as well as ceiling cassettes. Possible to use a combination of different type of heads, the residential wall mount units are not large as you suggest. Wall units are common because they’re easy to install- and that might be a consideration for you, too- Peter mentioned contractor ability.
Repurposing your archaic radiant system probably isn’t worth it. I’m not too familiar with radiant cooling, too humid in these parts. But, I’d think if IAQ is a concern, as Peter suggested, you’ll consider other options.