Are there ways to better conceal the ductless mini-splits hanging on walls? You still need an outdoor compressor unit sitting next to the home, right?

What are the advantages of either going mini-split or central A/C? Or can one do a combination of both? For areas that running HVAC ductwork that are difficult.

Yes Mini-splits still have a compressor, although you can run several interior units from one compressor. From an aesthetic and resale point the central system is more desireable. Consider building a bulkhead for hard to reach areas

Are there ways to better conceal the ductless mini-splits hanging on walls?

There are above-ceiling and in-wall units or "cassettes" as they are sometimes called.

You still need an outdoor compressor unit sitting next to the home, right?

Yes, there is an outdoor unit for the systems. You don't have to put them on a pad next to the home, there are wall brackets and I like to hang them beneath a roof overhang.

For areas that running HVAC ductwork that are difficult.

Seem to work well. I've seen them go in as upgrades in a lot of older places that never had any ductwork.

I will go with a central A/C system, I am not too keen on the way mini-splits look and the subsequent wiring and lines running down the homes wall and the unit sitting on the ground or even worse, the wall of the home.

We will have some challenges running the duct work through the InsulDeck. It's not just one main line but the 2nd return line.

Right now I am leaning towards a high-efficiency electric furnace with a heat pump backup and an ERV system. There will be NO gas coming to the home. Any suggestions to a good electric furnace and heat pump setup with an ERV?

THANKS

Lbear; the heat pump is the primary heating source until temperature dips too low and the electric resistance heat kicks in

the subsequent wiring and lines running down the homes wall

In new construction, the lines can run inside the walls where they are not visible.

We will have some challenges running the duct work through the InsulDeck

We just slid the appropriately sized PVC pipe into the utility chases to get instant ducting.

Right now I am leaning towards a high-efficiency electric furnace with a heat pump backup

Isn't it more efficient to have the heat pump as the primary source?

Posted By ICFHybrid on 13 May 2012 05:28 PM

We just slid the appropriately sized PVC pipe into the utility chases to get instant ducting.

Right now I am leaning towards a high-efficiency electric furnace with a heat pump backup

Isn't it more efficient to have the heat pump as the primary source?

Do you have any pics of the duct work install? Did you use PVC pipe instead of the typical duct piping? How big was the PVC pipe and what type was it?

The heat pump will be the primary source but as Chris mentioned above, the electric furnace would kick on when it gets really cold. Heat Pumps are good to around 20F and anything colder than that, they become inefficient. That is when the electric furnace would kick on and work more efficiently. The climate is moderate but there are days when it can get really cold (into the teens and single digits) and I would need the electric furnace for those nights.

Heat Pumps are good to around 20F and anything colder than that, they become inefficient. That is when the electric furnace would kick on and work more efficiently.

I think you will still get a good COP out of an air source heat pump even down at 20F. There have been some types discussed here that put out down to -4F. In any case, it's going to be better than an electric furnace which is never better than 1.0.

Do you have any pics of the duct work install?

It just shows a PVC pipe going into the end of an Insuldeck beam. It transitions to metal on both ends. It was regular plumbing pipe and it just fit in the large Insuldeck chase.

Posted By ICFHybrid on 13 May 2012 06:14 PM

Do you have any pics of the duct work install?

It just shows a PVC pipe going into the end of an Insuldeck beam. It transitions to metal on both ends. It was regular plumbing pipe and it just fit in the large Insuldeck chase.

So you just used a 3" PVC pipe as a HVAC duct? Do you lose any heating or cooling efficiency because of that pipe?

So you just used a 3" PVC pipe as a HVAC duct? Do you lose any heating or cooling efficiency because of that pipe?

4" Schedule 40 PVC. You could probably use an SDR35 sewer pipe, but we had the water pipe and we had to put it in in a hurry. The SDR35 pipe will rattle around in the chase a bit more because the OD is not quite as much as the Schedule 40 pipe.

I have no heating ducts. The house is all radiant and minisplit. The duct is for the ventilation system.

After the insuldeck is poured (and cured), you could use a hot knife to "square out" both of the circular chases together. That would get you a cavity big enough for a 6" X 12" rectangular duct.

Posted By ICFHybrid on 14 May 2012 01:36 AM

So you just used a 3" PVC pipe as a HVAC duct? Do you lose any heating or cooling efficiency because of that pipe?

4" Schedule 40 PVC. You could probably use an SDR35 sewer pipe, but we had the water pipe and we had to put it in in a hurry. The SDR35 pipe will rattle around in the chase a bit more because the OD is not quite as much as the Schedule 40 pipe.

I have no heating ducts. The house is all radiant and minisplit. The duct is for the ventilation system.

After the insuldeck is poured (and cured), you could use a hot knife to "square out" both of the circular chases together. That would get you a cavity big enough for a 6" X 12" rectangular duct.

So if I understand correctly, the reasoning for running the PVC as a HVAC duct is because the typical aluminum duct would get crushed by the weight of the concrete in the form, right?

So can radiant floor heating can provide enough heat to not have a HVAC vent in that portion/room of a home?

Did you run any plumbing runs DIAGONALLY through the I-beam of the InsulDeck area? Some say it is OK to do while others say it is not. Hard to get a solid answer.

Posted By ICFHybrid on 13 May 2012 06:14 PM

Heat Pumps are good to around 20F and anything colder than that, they become inefficient. That is when the electric furnace would kick on and work more efficiently.

I think you will still get a good COP out of an air source heat pump even down at 20F. There have been some types discussed here that put out down to -4F. In any case, it's going to be better than an electric furnace which is never better than 1.0.

Rheem and Trane now have Heat Pump systems that have a 10 HSPF rating / 19 SEER rating. They are very efficient.

The electric furnace would be an "emergency" back-up if something should fail or if it gets insanely cold (every 10 or so years it drops to -15F for a night or two), although it will warm up quite a bit in the day. An electric furnace runs for around $800, so it is cheap insurance.

If you are installing a split system heat pump, you don't need a separate electric furnace. All you need is the backup electric heat strips installed in the air handler. Both will operate at 100% efficiency (COP=1.0)

So if I understand correctly, the reasoning for running the PVC as a HVAC duct is because the typical aluminum duct would get crushed by the weight of the concrete in the form, right?

If you run duct of any kind in the Insuldeck chases, there will be no crushing as the foam does not deform before, during or after the pour. We used the PVC because we had it on hand and because of the transitions through the Insuldeck slab (web), where we didn't want concrete to metal duct contact.

So can radiant floor heating can provide enough heat to not have a HVAC vent in that portion/room of a home?

Yes. It is commonly done. If you have a tight home, you still need to provide for ventilation.

Did you run any plumbing runs DIAGONALLY through the I-beam of the InsulDeck area? Some say it is OK to do while others say it is not. Hard to get a solid answer.

No. You cannot violate the concrete portion of the Insuldeck structure. Vertical penetrations through the web are going to work, but NEVER through the I-beam portions without engineering review.

I am contemplating the same kind of heat/cool system for my 1100 sq/ft with a walkout basement (lakeside)... in my case I am going to include an electric furnace with a DC variable speed motor (with duct work) to circulate the air throughout the house year round and include a HRV; it will also serve to provide emergency heat when the temps get below the minimum for the mini-split (it regularly gets to -20f in Dec/Jan/Feb with lows of -35f so it will be using emerg heat regularly during those months).
Seems like the most bang for the buck to me in an area without access to natural gas. With the mini-splits running 8 or 9 months a year at a COP of greater than 1/1 I will only be paying for electric resistance heat at 1/1 for the coldest 3 months.....a HUGE savings over electric alone.
I like the idea of hiding the air handlers and wiring in the wall in new construction and will plan of doing this.

Seems like the most bang for the buck to me in an area without access to natural gas.

Does that mean no propane available either, or does the price of propane point to electric resistance heat?

Posted By ICFHybrid on 14 May 2012 03:01 PM

Seems like the most bang for the buck to me in an area without access to natural gas.

Does that mean no propane available either, or does the price of propane point to electric resistance heat?

For me, the area does not have natural gas but propane tanks are an option. It is not economical to buy a tank and have a company come out and pump the tank full of propane every month or so. Costs are equal or greater than electricity.

In addition I am not comfortable with a propane tank sitting next to the home and having gas lines snake their way through the home and its walls. I had to deal with a gas leak in my previous home and it almost turned into a deadly disaster. Even the home I am in now has natural gas and I had a leak to deal with. Luckily I was home and found it quickly before it leveled my home. So for my future home I just prefer not to deal with it. Yes, I know millions of people have gas and it is relatively safe but it's just my choice. The icing on the cake is the costs of propane skyrocketed. It's no longer less expensive to heat with propane in my area, as electricity is cheaper.

I just looked at the data on the Miitsubshi line and one of their their best minisplits will provide 22,500 BTU/h at 5deg F and provide 18,000 BTU/h at -13 deg f. This unit sells for less than $2000. I doubt I'll need to ever resort to resistance heaters as my design heat loss at -10 deg f is 12,000BTU/h. I'll tolerate the ugly interior unit for that kind of performance. BTW there is a line of PVC fittings for SDR 81 PVC pipe that are very close in size to conventional metal duct sizes ie 6" is 6"id unlike ips sizes.

Which brings me to my next question. If I have an ERV hooked-up to the central A/C, do I still have to VENT the bathroom areas through the roof?

The master bath will be completely open design with no doors as the flow from the master bedroom to the master bath. If that area has vents for the HVAC with an ERV system hooked to it, do I still need to vent the bathroom through the roof?

We have done it both ways. ERV/HRV pulls from the bathrooms and kitchen and replaces in the bedrooms and living. However some designers do not like pulling the really moist air through the ERV/HRV and prefer to still use a bath fan. Even with a central system, we still prefer to pipe the ERV/HRV separate and not use the ductwork from the central system. It makes the ERV/HRV more efficient and the furnace fan does not have to run when the ERV is as well. Also I did not know Mitsubishi H2 units were available in a 2 ton application. I thought it was just 1 ton and 3/4 ton for the single head units, and then a 3 ton unit with twinable heads.