High Velocity Space Pak HVAC Eichler installation

High Velocity Space Pak HVAC Eichler installation

We ended up going with the Space Pak brand of high-velocity HVAC system instead of Unico due to a few aspects that make the installation cleaner (duct fasteners) – and because the rep was more knowledgeable and willing to work with our HVAC installer than the Unico rep. All of the research I did showed that there wasn’t much difference between the two so either would be a fine choice. Attched are couple pics of the ductwork on our roof. The green layer is a sheetrock-like, fire-retardant 1/2″ material called DensDeck that was required by the fire inspector to meet fire codes. It cost about $5k installed (~$20/sheet). We also have a fire sprinkler system on the roof which is now covered with metal for protection (per building dept request) – our roof is a very busy place! We hope to pass all of our inspections and get the foam sprayed on this week before it starts raining!

Update: We have the spacepak system installed and running now. We went w/ a 4 ton, 2 zone system with honeywell programmable thermostats and I have to say that it is pretty great. It keeps the house very comfortable whether warming or cooling.

It does make a whooshing sound when it’s running which seemed pretty loud at first, but we’ve gotten used to it and it’s certainly tolerable.

The cooling works especially well because of the wind-chill factor the cold air has coming out of the vents.

I still need to take some pics of the heat pump and blower, but I’ve attached pics of the duct work on the roof before it was covered in foam. The big, angular metal is covering the fire sprinkler pipe, and the smaller angle metal covers the new wiring.

I’m happy to answer any questions people may have.

Update: Thought I’d post an update w/ my thoughts about our HVAC system after living w/ it for almost a year.

I really like the zoned system and the programmable thermostats since we can fine tune the precise temps for different parts of the house at different times of the day w/ energy conservation in mind.

Another thing I really like is that the air is circulated often which prevents condensation on the windows and skylights – especially in the bathrooms after showers.

Temps remain consistent throughout the year.


The air is pretty loud coming out through the vents – one reason for us, is that w/ a zoned system all of the air is forced through half of the house at once. It is very rare for both zones to be going at the same time, because of this, I’m thinking we could probably cut our tonnage in half for the heat pump and air handler. I’m not 100% sure, but I think the system is probably ‘short cycling’ because of this as well.

The heat pump outside can get pretty loud when it’s really cold or hot outside. We don’t hear it in our house, but I would prefer if it were quieter. I’ve taken some steps to sound proof it, and plan to do more.

Our electricity bill doubled last month when we had a week of freezing temps because the heat pump was running around the clock. I’m sure everyone experiences this to a certain degree.

1. If you’re doing a zoned system take what I mention above about tonnage into consideration and discuss w/ your HVAC contractor.
2. Make sure your HVAC contractor adjusts the zones so that the inactive zone is actually 10% open to allow excess pressure to escape instead of forcing all the air through the active zone. We plan to have this adjusted on ours which should help reduce the noise.

Update: Also attached a pic of how the air vents look inside the house. They also offer a choice that looks like a mail slot instead of a circular hole.


11 thoughts on “High Velocity Space Pak HVAC Eichler installation

  1. I believe you have picked up more noise from the sheet metal trunk line or supply line. Since Space Pak came out they always have recommended the fiberglass trunk line. Within the last handful of years they have offered up some trunk line options like sheet metal and special plastic sections. They have since stopped offering up the plastic option and are now left with fiberglass and metal. The fiberglass trunk line aids in sound deadening since it is like an insulation. It looks like you did not have much choice though the way the roof is set up. The company that installed it may be able to lower the static pressure by adding a blocking plate or sheet metal spear into the existing trunk line about 12 inches from the air handler. Lowering the static pressure will make the system run more quietly, but will also effect performance. Also you may have to let more than 10% of that air by pass when the one out of the two zones are only being used. Just a few thoughts on how you may be able to make the system quieter.

    1. Hi Ted,
      Thank you soo much for providing this valuable feedback!

      I will consider your suggestions carefully – it would be great if we could make it a little quieter.

      We just had the first hot weekend of the year, and it was very nice when the AC kicked in. 🙂

  2. Hello
    Could you please tell me the company you used to install the system? We live in the East Bay and am having trouble finding an experienced installer.


    1. Hi Vini,
      I recommend Downing HVAC: http://www.downinghvac.com

      They didn’t do the original install (can’t recommend the installer we used), but they provided great service when we added a heater strip module to our blower (kicks in when heat pump needs to defrost on very cold days).


  3. Steve,
    Thank you so much for responding. One more question…I called one of the companies recommended by SpacePak and they said they charge $140/hr and it will take 6-8 hours for them to do an evaluation and provide me with an estimate.
    Does that sound right? So I have to spend $1000 or so just to figure out whether the system is right for my house…?
    Thanks again.

    1. Seems a little much to me. Most companies will do a free estimate. Downing did for us. We ended up choosing a cheaper installer and regretted it. Downing had to come out to fix the system just to make it work. We wished we’d gone with them for the installation in the end. High velocity systems are much more complex than regular forced-air, so make sure you choose someone that has a proven track record, and call the references they give you. Downing uses Unico instead of Spacepak, but they are very similar systems. I think unico formed from some of the original owners of spacepak or something.

  4. I just installed a Spacepak system. I installed it myself. I had no experience in A/C and i used the Spacepak documentation in order to size it and to install it . It’s a 2 storey home( 2200 sq. Ft). 2 1/2 tons. i have 9 outlets upstairs and 6 downstairs. The system is located in the attic. It is cool upstairs. It is a little bit noisy but the temperature is the same everywhere. I bought it from 1 source2buy.com. I hire a contractor to install the A/C unit (condenser).

  5. Hi, do you have a picture of what the roof looks like after the foam got sprayed? I just bought an Eichler home that has forced air heat/cooling with the large circular ducts. I am considering replacing them with the slim ducts that you have and then covering them with the foam. Thank you.

    1. Hi Stef,
      Our roof ended up pretty lumpy due to a poor choice in roofing contractors – it works great, but isn’t very pretty. There are steps that a good roofer will take to make it as smooth as possible, but you should expect some lumpiness when you are burying stuff in the foam. One approach they take is to cut out styrofoam type stuff into puzzle shapes to put inbetween the ducts to get as close to a flat surface as possible before spraying the final foam layer. We just filled in all the gaps with spray foam so it’s like 6 inches thick instead of the standard two inches. Great insulation, but uses a lot of spray material..

      I’m fan of spray foam on flat roofs – no leaks!

      Best of luck!

  6. Hi Steve, I’m about to install a Spacepak system on our Eichler and found your page while looking for help on placing vents. I didn’t realize so many were required! Our contractor calculated we need 29 for our 1800 sq ft house. Anyways, it’s hard to find so many places where the air won’t be blowing directly on something or someone. I was wondering in general where you placed yours (toward the walls or toward the center) and if it’s annoying to have the air blow directly on you while on the couch, bed, or desk. Also, I see you placed some near the windows with vertical blinds. Does it knock the blinds around? We’re thinking of similar placement. Thanks for any advice! Fun that this post keeps on giving so many years later.

    1. Hi Albert
      I’m glad this post is still useful.

      You’re asking a great question, one that I wish I had asked. Our installer thought it best to install all of the holes close to the exterior walls/windows thinking that is where the heat/cool comes from, and I think that does make sense.

      It does defog the big windows which is nice.

      However, you should definitely try to avoid having them directly over the beds as the heat cycle creates a draft that feels cold which can be unpleasant.

      Conversely, I LOVE the feeling of the cold AC air blowing directly on me when on the couch in the summer, or working in the office – and it doesn’t bother me during heating in the winter.

      The blinds shimmer a little but they don’t move enough to be annoying.

      The other thing that I think about is the noise level, I wonder if we over sized our blower and if a smaller one would reduce the air pressure a bit. We have to turn up the tv a couple clicks when it comes on.

      If you can get a blower that is configured to handle zones, that would be cool instead of it blowing all the pressure through half the holes when only one zone is going. Definitely glad we have the zones tho since we only heat the bedrooms on cold winter nites, and only cool the living areas in the summer.

      Overall we have been very happy w/ our system.


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