Mini-split for whole house?

[pronstar]

…or at least 2/3rds of a house.
As we begin to plan the upgrades to our house, one of the first things I need to address is our HVAC.

We have two stories, so an upstairs and downstairs unit.

The upstairs unit is a central-air heat pump unit, and it works great.

The downstairs system is a traditional central-air setup, but it was built with no air returns. So the closet-located air handler only draws air from a vent that’s immediately below it.

I’m just weighing options, and am wondering what the pros/cons are of a ductless mini split with several heads vs central air for a large-ish first floor?

In the summer we use 6,000 kWh per month so anything that can reduce those consumption would be great.

 

[Ace in the Hole]

…or at least 2/3rds of a house.
As we begin to plan the upgrades to our house, one of the first things I need to address is our HVAC.

We have two stories, so an upstairs and downstairs unit.

The upstairs unit is a central-air heat pump unit, and it works great.

The downstairs system is a traditional central-air setup, but it was built with no air returns. So the closet-located air handler only draws air from a vent that’s immediately below it.

I’m just weighing options, and am wondering what the pros/cons are of a ductless mini split with several heads vs central air for a large-ish first floor?

In the summer we use 6,000 kWh per month so anything that can reduce those consumption would be great.

In Texas adding insulation, solar attic fans, and radiant barrier will drop your usage drastically. Updating and balancing your ac system will save a ton as well. If you do the upgrades and insulation there are credits and rebates in Texas. I’ll pm you later on it.

If you want radiant barrier I’ll ship you what you need at my cost for the stuff I have manufactured. Single best thing to do in Texas IMO

 

[Waterjunky]

Yea, it can be done fairly easily. I am looking at potentially doing it to my house. One of the advantages is that each room is now individual in its control. Extreme zone control. An additional advantage is if one goes down, it will only take down part of the house. The other is still quite livable. I was considering several units that could support up to four (I believe) heads each. My house is about 4K sqft.

 

[SoCalDave]

We're in the process of adding about 900sqft and I'm going with multi zone mini split systems on the addition and will most likely do the other 1100sqft with one as well.
Best thing about them are they are inverter compressors and you only cool/heat the room needed, not the whole house. Probably go with Daikin as they have good reviews.

 

[Morehart]

I would look into a vrf system

 

[sirbob]

I have a Daikin - I love it...

However, the model I have does not stay running more than 24 hrs (or possibly less - it times out) and does not have a remote (read off-site) control. It does have an actual hand remote to turn it on etc.

So its good while I'm in the room but not something I can use to heat or cool if I'm not there to turn it on each day.

If you need the heating part - it won't work in extreme conditions i.e. colder than mid 40s. It doesen't actually heat.

 

[SoCalDave]

New generation ones have Bluetooth to operate them when offsite. They also have occupancy sensors built into the head units so when no one is present for more then 20 minutes the units goes into power saving mode.
I'm in SoCal about 5 miles from the beach so not worried about the heating portion as it wouldn't get turned on often.

 

[pronstar]

In Texas adding insulation, solar attic fans, and radiant barrier will drop your usage drastically. Updating and balancing your ac system will save a ton as well. If you do the upgrades and insulation there are credits and rebates in Texas. I’ll pm you later on it.

If you want radiant barrier I’ll ship you what you need at my cost for the stuff I have manufactured. Single best thing to do in Texas IMO

Thanks!
Yeah upgrading insulation is definitely needed, thanks for the rebate tip.

I’ll definitely take a look at radiant barrier…we bought the house as a fixer and I want to rebuild it correctly, as there’s a buttload of half-assed shit I need to correct.

 

[rrrr]

Thanks!
Yeah upgrading insulation is definitely needed, thanks for the rebate tip.

I’ll definitely take a look at radiant barrier…we bought the house as a fixer and I want to rebuild it correctly, as there’s a buttload of half-assed shit I need to correct.

How old are the windows? Those aluminum frame sliders put in during the last century leak like crazy.

You probably know this, the bazillion window replacement companies in North Texas want around $1,200 per window. I installed double pane aluminum frame windows in our house in 1998. Vinyl windows didn't exist then. I looked into replacing mine before we sold the house, and decided eff that.

 

[Waterjunky]

The ones I am looking at are actually designed for whole house / larger areas. They function like a normal HVAC in that regard. No odd timers and they will run down to close to 0F before they get weird.

 

[Ace in the Hole]

How old are the windows? Those aluminum frame sliders put in during the last century leak like crazy.

You probably know this, the bazillion window replacement companies in North Texas want around $1,200 per window. I installed double pane aluminum frame windows in our house in 1998. Vinyl windows didn't exist then. I looked into replacing mine before we sold the house, and decided eff that.

I have them made in San Antonio...average cost $250-500 depending on size. @pronstar you would have to go pick them up though. 6-12 week lead time. That cost is for white vinyl. Some windows will cost less or more. I can arrange an installer as well that I've worked with. Windows and insulation were my biggest profit makers in TX on our efficiency packages.

 

[Ace in the Hole]

Thanks!
Yeah upgrading insulation is definitely needed, thanks for the rebate tip.

I’ll definitely take a look at radiant barrier…we bought the house as a fixer and I want to rebuild it correctly, as there’s a buttload of half-assed shit I need to correct.

Energy Efficient Products: Radiant Barrier, Spray Foam Insulation, Attic Fans

www.energyefficientsolutions.com

I work with these guys, Idk if they sell direct to public. I have an account and can assist if they don't.

 

[pronstar]

I would look into a vrf system

What dat?

 

[Morehart]

Variable refrigerant flow. Allows multiple fan coils in each room. Some rooms can heat or cool to different temperatures. Also very efficient

 

[Morehart]

Or you could just run a 4 zone minisplit

 

[pronstar]

I have them made in San Antonio...average cost $250-500 depending on size. @pronstar you would have to go pick them up though. 6-12 week lead time. That cost is for white vinyl. Some windows will cost less or more. I can arrange an installer as well that I've worked with. Windows and insulation were my biggest profit makers in TX on our efficiency packages.

So we replaced 11 windows almost 2 years ago, mostly because the old ones were original non-tempered single-pane and we had kids on the way. Way too dangerous.

New vinyl, double-pane and energy efficient. And the energy efficiency is a bonus.

Basically all these you can see here, plus a few not visible here. Cost me $4k installed, contractor pricing as I used the same company for my flips.

This is my other challenge…all glass, faces west and no shade, so it’s all sun and all heat in the summer. The glass is very old and double-pane, but lets massive heat inside.

We need to figure out if we want to keep/replace the glass, or make it a more traditional wall with windows.

 

[SoCalDave]

I was doing some electrical at an older house in LB and the neighbor had a Mitsubishi one and I tell ya that thing was so quite you didn't even know it was running.
Looked to be a four zone.

 

[SoCalDave]

So we replaced 11 windows almost 2 years ago, mostly because the old ones were original non-tempered single-pane and we had kids on the way. Way too dangerous.

New vinyl, double-pane and energy efficient. And the energy efficiency is a bonus.

Basically all these you can see here, plus a few not visible here. Cost me $4k installed, contractor pricing as I used the same company for my flips.

View attachment 1164640

This is my other challenge…all glass, faces west and no shade, so it’s all sun and all heat in the summer. The glass is very old and double-pane, but lets massive heat inside.

We need to figure out if we want to keep/replace the glass, or make it a more traditional wall with windows.

View attachment 1164641

Yeah that top rooms gotta be cooking in the summer. Maybe some outdoor remote controlled power shades to block the sun in the afternoon?

 

[pronstar]

Or you could just run a 4 zone minisplit

That’s what I’m considering in this thread, ductless with multiple heads

 

[SoCalDave]

They do make 5 zone units as well...

 

[pronstar]

Yeah that top rooms gotta be cooking in the summer. Maybe some outdoor remote controlled power shades to block the sun in the afternoon?

The upstairs unit works well but you’re absolutely right, it’s a helluva heat load.

For the lower level, that whole run of glass was an addition, and there’s exactly one vent register. It’s a big problem, especially with no air returns.

 

[Boat 405]

I have a multi zone unit that does 3 bedrooms and it's fantastic. Then 1 larger unit for the general living area/kitchen.

 

[pronstar]

I have a multi zone unit that does 3 bedrooms and it's fantastic. Then 1 larger unit for the general living area/kitchen.

Did you notice a difference in your power bill?
I’ve read that the newer minis are 30-40% more efficient than conventional.

 

[Boat 405]

Did you notice a difference in your power bill?
I’ve read that the newer minis are 30-40% more efficient than conventional.

Oh it was significant. Close to $800 a month. Now like $300-$400 a month. Used to have to run the old whole house unit all day to keep temps. Now i can run a single room for 15 mins and cool it when i get home.

 

[pronstar]

Oh it was significant. Close to $800 a month. Now like $300-$400 a month. Used to have to run the old whole house unit all day to keep temps. Now i can run a single room for 15 mins and cool it when i get home.

As I understand it, they’re basically inverters and can run at variable speeds.
I’m intrigued…I’ll mindfuck this decision for a few more months LOL

 

[coolchange]

I

I was doing some electrical at an older house in LB and the neighbor had a Mitsubishi one and I tell ya that thing was so quite you didn't even know it was running.
Looked to be a four zone.

have big 3 phase at work and it’s the same, I can’t tell it’s running.

 

[Ace in the Hole]

Did you notice a difference in your power bill?
I’ve read that the newer minis are 30-40% more efficient than conventional.

Increased seer rating in a central unit will have a similar effect. We had a 16 year old unit in the house in havasu...upgraded to the 17 seer 5 ton during the full gut job,. Utilities dropped like a rock. Im installing radiant barrier this winter in the house along with 3 attic fans and some addl insulation. That ought to drop it even more. I have a goal to get the havasu summer bill to under $200 with the pool etc.. We run the house at 74, bedroom portable at 66 (when we are there), and the garage at 78. I think its going to get there. Then I'll solar for the remainder.

Efficiency on central ac units make a major difference.

 

[CSmith]

What dat?

Variable Refrigerant Flow

Depending on how it is set up you have 1 condensor outside with multiple heads indoors. You can heat and cool certain rooms at the same time. Or have different target temps. Or if it is a straight heat pump set up than you can only cool or only heat the multiple different heads.

 

[Riverbound]

There are many many many ways to skin this cat. Based on the information you posted so far.

To achieve everything you discussed you dot. Have to go ductless.

My initial recommendation would be a simple set up where you have constant air movement and 18-20+ seer units with constant air movement utilizing existing ducting and architecture of home.

 

[Looking Glass]

So we replaced 11 windows almost 2 years ago, mostly because the old ones were original non-tempered single-pane and we had kids on the way. Way too dangerous.

New vinyl, double-pane and energy efficient. And the energy efficiency is a bonus.

Basically all these you can see here, plus a few not visible here. Cost me $4k installed, contractor pricing as I used the same company for my flips.

View attachment 1164640

This is my other challenge…all glass, faces west and no shade, so it’s all sun and all heat in the summer. The glass is very old and double-pane, but lets massive heat inside.

We need to figure out if we want to keep/replace the glass, or make it a more traditional wall with windows.

View attachment 1164641

OUCH!! Have you ever looked into or thought about those Roller Shades? The ones I have seen here in Arizona are nice and can be on a "Remote Control" also.

 

[McKay]

I have a conventional system in my house. But between some areas in the house and shop I have added a total of 10 mini split head units. Some on single condensers and some with 4 heads per condenser. If I were ever to build a new place I would do the whole house with them.

 

[Uncle Dave]

I like minis. I have many friends with them. They like them.

Variable control per room is great - there is always that "hot /cold room" in a house.
Of course a multi head w/one compressor you cant vary too much, but the hot room can certainly increase airflow.

The downsides - they dont really have good filtration, if any. Some have the plastic mesh that doesn't trap shit.
Check out a place with them running continuously there are always dirt streaks in the handlers, and you have to clean them religiously or they can mold.

My central unit has an incredible 16x25x5" thick merv 16 carbon filter that even removes smoke.
I go back and forth on splits vs a big high seer 5 ton variable speed fan and variable compressor unit.

Get an attic fan (do the math on the net square inches of vent space vs CFM) and maybe a whole house fan and insulate like your life depends on it. I'd bet you can cut the Ac load in half with a cool roof but thats a significant spend as is solar.

6K KW is a 25-2700 bill here.

 

[pronstar]

6K KW is a 25-2700 bill here.

Wow, that’s crazy.
I’m at $800 for 6 kWh which is 1/3 as crazy…yikes

 

[bilz]

Two compressors one for kitchen and lr, one to handle each of 3 bedrooms. Went with daiken, and absolutely love it. Cool only the rooms you want, and cool them fast. You can set timers to turn on daily at specific time. My son sets his for ten minutes before home from work.

 

[pwerwagn]

I’ll mindfuck this decision for a few more months LOL

Please do...and keep this thread updated so I dont have to start my own lol.

 

[pronstar]

I think our permitting (6 months and counting) for our garage conversion is close to complete. It’s for the in-laws.

It’s 700 square feet and will have one bedroom.
For sure I’m going with a ductless mini split.
I suppose it’ll be a trial run for the rest of the first floor.

Another reason why I’m leaning toward mini splits is because this downstairs unit ain’t gonna last, and will need to be replaced before we are ready to renovate the entire first floor…so I won’t have tear up my drywall to run air returns.

 

[SoCalDave]

Now here's my next decision, wall mount, cassette mount or concealed duct.
Without a doubt wall mount is the easiest to install if you can live with the unit hanging on your wall.
I'm thinking cassette or concealed for my new addition and when the time comes retrofit the existing house with wall mount.

 

[Waterjunky]

If your a little crafty, you could get real filters in the concealed......

Big deal for me. My guess is it is for most on here.

 

[Fastdadtsmith]

I just love all these options for the DIY peeps to save some money.

 

[boatdoc55]

In Texas adding insulation, solar attic fans, and radiant barrier will drop your usage drastically. Updating and balancing your ac system will save a ton as well. If you do the upgrades and insulation there are credits and rebates in Texas. I’ll pm you later on it.

If you want radiant barrier I’ll ship you what you need at my cost for the stuff I have manufactured. Single best thing to do in Texas IMO

Solar attic fans?? Do those really work? I'd be interested in those here in Havasu.

 

[Cobalt232]

When we built out new darkrooms for some processing equipment, we put Daiken mini splits in 3 of the rooms. They run off of a single compressor on the roof. They work really well, however, we did learn that they all have to be heating or cooling, in other words, one can't heat and one cool at the same time. They work great as we can keep the darkrooms negatively pressured, so they don't mix their room air with other rooms, we just had to account for proper makeup air.

 

[pronstar]

I just love all these options for the DIY peeps to save some money.

Who said anything about DIY?
Zero chance I’m doing this myself.

 

[DirtyWhiteDog]

For the pro's in here ?
If you're changing your FAU's to high efficiency unit (s), what are your thoughts on removing all attic insulation, sealing all roof and soffit vents. Then installing R-38 or better directly to the underside of the roofline ?
Basically converting an existing house to a cocoon system. Obviously would only work in a dryer climate. I see 80%+ of new houses in the Vegas area built with no roof venting.

 

[SoCalDave]

Who said anything about DIY?
Zero chance I’m doing this myself.

Mr Cool makes DIY systems...

 

[Ace in the Hole]

Solar attic fans?? Do those really work? I'd be interested in those here in Havasu.

We did a lot of trial and error testing before we advertised them. Short answer is yes as they will move a lot of air. Longer answer is that it isn't just a slap it on and all good scenario. Having enough blown in insulation, to keep the heat from the attic out is part of the equation. Second part is reducing the radiant heat from the actual roof...using radiant barrier. Third component is removing the hot air that is left.. You need to move enough air to be effective. I've seen attic temps drop 40+ degrees with a combo of all three in the south texas summers.... One of my winter projects is doing this in havasu. It's going to get the treatment this winter...new insulation, my radiant barrier product, and fans mounted at the grate of each gable (3). Off the shelf solar attic fans aren't crazy expensive if you have a shingle roof....when it comes to tile, it's a different install method (use existing vents etc). In two story homes that would have in some cases a 10+ degree difference in temps upstairs and down stairs...we would have those to the low single digits... We had data showing 20-30% reduction in kWh usage as well.

I can get pretty in depth on the details but thats the basics. I've got some cool FLIR photos as well. In Texas we didn't have the roof space to knock out utility bills with just solar....so we got creative and found solutions to reduce consumption. Around half of my deals used to include some form of efficiency package. "The Utility Roundhouse" as it was called rolled the attic package in, with solar, new HVAC, and windows. It was meant to be a play on giving the utility a roundhouse kick to the face...and we advertised it as such. It was effective...and saved people money vs overselling solar. Our margins were not impacted in a negative way either.

Radiant heat from your roof/attic is a major drain on HVAC efficiency.

Install in progress a few years back. Alamo Heights, TX. 2 story with a major temp difference. 1st photo is standard, second is thermal. Its a night and day difference. 3rd photo is same house, but different section in progress..also thermal.

 

[pronstar]

We did a lot of trial and error testing before we advertised them. Short answer is yes as they will move a lot of air. Longer answer is that it isn't just a slap it on and all good scenario. Having enough blown in insulation, to keep the heat from the attic out is part of the equation. Second part is reducing the radiant heat from the actual roof...using radiant barrier. Third component is removing the hot air that is left.. You need to move enough air to be effective. I've seen attic temps drop 40+ degrees with a combo of all three in the south texas summers.... One of my winter projects is doing this in havasu. It's going to get the treatment this winter...new insulation, my radiant barrier product, and fans mounted at the grate of each gable (3). Off the shelf solar attic fans aren't crazy expensive if you have a shingle roof....when it comes to tile, it's a different install method (use existing vents etc). In two story homes that would have in some cases a 10+ degree difference in temps upstairs and down stairs...we would have those to the low single digits... We had data showing 20-30% reduction in kWh usage as well.

I can get pretty in depth on the details but thats the basics. I've got some cool FLIR photos as well. In Texas we didn't have the roof space to knock out utility bills with just solar....so we got creative and found solutions to reduce consumption. Around half of my deals used to include some form of efficiency package. "The Utility Roundhouse" as it was called rolled the attic package in, with solar, new HVAC, and windows. It was meant to be a play on giving the utility a roundhouse kick to the face...and we advertised it as such. It was effective...and saved people money vs overselling solar. Our margins were not impacted in a negative way either.

Radiant heat from your roof/attic is a major drain on HVAC efficiency.

Install in progress a few years back. Alamo Heights, TX. 2 story with a major temp difference. 1st photo is standard, second is thermal. Its a night and day difference. 3rd photo is same house, but different section in progress..also thermal.
View attachment 1164994
View attachment 1164995
View attachment 1164996

Vented ridge?

Any issues with conventional hvac upstairs, and mini splits downstairs?

 

[Ace in the Hole]

Vented ridge?

Some have them some don't. We would not add them for liability reasons. However if you have a vented ridge that will improve the efficiency as well..it creates more air movement. The air between the radiant barrier and roof itself, will be drawn up and out of that vent. If a home had a ridge vent we would typically use an internally mounted fan to move air in the attic...or if there was a ridge vent, and traditional vents we would pull a couple traditional ones and install solar ones for a similar effect. When installing radiant barrier the fan type makes a difference on where we will have gaps etc for air movement. Kinda like I put above its not really just a slap them on solution..though the fans by themselves will drop your temps enough to notice a few % drop in consumption on their own. They really shine when you put them together with the other attic efficiency items.

In the FLIR photos, the space at the ridge shown is what you would typically leave open for a home with a ridge vent.

 

[pronstar]

In the FLIR photos, the space at the ridge shown is what you would typically leave open for a home with a ridge vent.

It looks like the radiant barrier stops at the ridge. How come you didn’t run the radiant barrier all the way up?

 

[Ace in the Hole]

It looks like the radiant barrier stops at the ridge. How come you didn’t run the radiant barrier all the way up?

On that particular house, airflow. The air between the barrier and decking gets very hot & you have to get it out or you can peel shingles. A layer was installed later that created a “duct” with a solar fan blowing it out a vent at the gable end. I unfortunately don’t have a picture of that. I’ll add a diagram to this thread later on how it worked. That home was over 100 years old and on projects like that we kind of have to think outside the box

In a home with a ridge vent in n most cases I’m going to run it all the way up to about a foot from peak as the vent will pull out the air. Every house is going to have some quirk.

 

[Ace in the Hole]

Any issues with conventional hvac upstairs, and mini splits downstairs?

Nope…it will make your upstairs one work less, and be more efficient. In the summer the consumption drop after attic work is very evident on the utility bill. The vast majority of homes we did this to had hvac in attic.