Opinions on this HVAC Design
Hi, I got an HVAC design complete as per my City requirement for permit application. I am building a two story, slab on grade house with the follow value; slab: R-32, wall: R-60, ceiling: R-90 and ACH: 0.6.
They provided the attached design with the following response below. I am concern this is over kill, especially the posted 6kW inline Thermo-Air heater since base on my heat load calculation, my house would require around 33-35k BTU. Any feedback and suggestion would be welcomed.
“Frankly, one unit for each floor is not the best way to heat. Because you will have an air heater on the HRV and your R-values are really good, it may work. The best way I think; installing small heat pumps for each bedroom, one big for the living room kitchen area and one small for the flex room. There are outside units with 5 indoor heads you can use. Also, I would install an electric baseboard heater in the laundry room and in floor heating for bathrooms.”
Thank you, Arnold
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Replies
Did you do a per room Manual J + S, T, D?
Hi Jon,
I have not yet received anything except the above attachment from the HVAC designer but I did my own to compare since I don't have a lot of confidence in many of the trades around my area for anything beyond code minimum.
Attached is the heat load I came up with which is within the range I was expecting so I think it 90%+ accurate.
Thank you,
Arnold
> air heater on the HRV
So all of the CFM listed are flowing through the HRV (ie, outside air)? Heat from the mini-split is accounted for? My initial reaction would be to use a single head ducted mini-split and a separate ventilation air system (with much lower CFM).
Hi Jon,
列出的CFM正在通过HRV进行外部空气。我的妻子开始考虑使用一个隐藏的两个天花板和单独的管道系统上的HRV使用管道的迷你放热泵系统。
We initially wanted to go with ductless mini split system but it is proving to difficult especially with the heat source in each room that is required by the Ontario code.
I am open to anything that would work for our situation without it being overkill and inefficient.
Thank you,
Arnold
我猜你可以加热和冷却with an oversized HRV+coil unit but it makes no sense from energy point of view. That much fresh air would definitely make for great indoor air quality though.
Cooling and heating flow rates are much higher than what you need for ventilation, there is no point in bringing that much fresh air into the house.
The simplest is to go for a ducted mini split for heat and cooling and keep the ventilation separate.
You can usually skip the post heater for the HRV if with a higher performance unit and good register location. Go for one with mid 80 efficiency, place the fresh air supplies register up high on the wall, blowing along the ceiling and away from where people will sit. Even if you are going with a duct heater, you would be looking around 1.5kW unit max.
如图所示，您可以用两个壁挂式迷你拆分加热房屋，您还必须在每个关闭的房间中安装踢脚板加热器，以使建筑官员满意。这些不需要太多，运营成本将很少，它们只需要证明足够的热量即可均能降低室温。
The issue with this type of layout is cooling. The bedrooms would be too hot unless the doors are kept open. For the bedrooms at least, a ducted unit is the best way to go.
The loss numbers also seem a bit on the high side based on the size and description of the building. I would guess it would be closer or bellow 24000BTU.
Hi Akos,
Thank you for your response. I ran the number for my heat/cool load and notice an error on my part and the total heat load is now 29,200 BTU/h. I have updated the attachment in my original post.
The post inline heater was simply added to satisfy the heat source in each room that the building code requires and I was planning on going with a 1kw. I would only use it on the very cold days if the wood stove isn't enough.
We're starting to think we may need to go with a duct mini-split despite not being out top choice for cost and efficiency. I guess we dropped the ball on this and assumed two wall unit would be sufficient to comfortably distribute evenly to provide a good occupant comfort.
有人有天花板单位的经验吗？我认为也许我们可以使用一个天花板安装座来帮助更均匀地分配热量和凉爽的空气。这是拟议的布局。
谢谢，
Arnold
Our ceiling mount has worked well. Looks a lot nicer and seems to work just as well as the wall units. I wouldn't say it works any better, seems to be more for looks. Install is of a course a bit more difficult but it didn't make much difference in the price. I did get an external thermostat for it but even without it set points and comfort were pretty good. Our install location has it near a bunch of windows in a larger room so opted for it just to be safe. The combo of ceiling mount in the main living area and a ducted system for the bedrooms has worked very well overall.
Hi Dan,
Thank you so much for that feedback.
Arnold
If you are planning some in floor heat the best way to make the inspector happy would be to put a token amount of in floor hear in each room all controlled by the bathroom thermostat. I doubt the inspector has much code language about how much heat is required per room to give you a hard time, just show some and you could include a switch to turn it off.
Give your insulation levels, assuming no huge windows and if you tend to keep the doors open most of the time I doubt you will see much room to room temperature variation.
您为什么认为洗衣房需要自己的加热器？
您多么确定，加热的浴室地板可能会被使用？我了解这听起来很豪华，但我怀疑当我认为它们的成本是热泵的4倍时，我会关闭它们。
Walta
Hi Walta,
We have no intention of putting in floor heating and it was the HVAC designer who was suggesting we install them to heat either the entire second floor or just to ensuite.
The laundry/utility, again the HVAC designer indicated because of the amount of exterior wall to square footage, it would need some type of heater which he suggested a baseboard.
We are starting to lean towards doing a two zone ducted ceiling concealed unit, one each floor.
问题是，我怀疑这位HVAC设计师在高节能的房屋设计方面没有任何真正的经验，并且正在尺寸尺寸。这是我不是很熟悉的一个建筑领域，并希望“专业人士”能帮助我，但在这个论坛上的大家帮助下，坚持自己分发它。说租约非常令人沮丧。
Thank you,
Arnold
请注意，如果没有热源，关闭的房间就无法获得足够的热量 - 这不仅仅是“满足愚蠢的代码”的东西。另请注意，如果该房间像房屋的其余部分一样温暖，那么所谓的“补充”房间的热源将提供100％的房间热量。摘要：在每个房间使用带有管道的1：1小型切片（或两个）。如果房间加载不同的位置，则使用分区（带有恒温控制的部分阻尼器）。
Hi Jon,
We are starting to about doing a two zone Mitsubishi Ceiling-Concealed Style unit, one for each floor and put those two unit in utility room where we have access for servicing. We're hoping the 16" O.C. joist can be used to run the ducts and out through either the ceiling for the first floor or the walls on the second floor.
Thank you,
Arnold
We're now strongly looking at a ducted system by using two ceiling concealed units, one for each floor but have them both installed in the utility room for easy service access.
The hope is to run the ducts in the between the 16" O.C. floor joist with the diffusers coming down from the ceiling for the first floor and out the top of the walls for the second floor. I attached a very rough diagram for those who are visual.
- 如果这种方法可行或推荐？
- 您可以在2x4分隔的墙壁上运行管道吗？
Thank you,
Arnold
通常不是沿着地板托梁运行管道的问题。选择i-to-toiist或地板桁架可以简化跑步，因为您可以运行垂直于托梁的管道。用硬管横穿i-tosist或桁架是坚硬的，flex是最简单的，请确保相应地尺寸的管道尺寸，以获得额外的损失。
For the 2nd floor, the simplest is to drop the ceiling in the hallway a foot and mount the unit there. From there you have pretty simple runs to all the rooms nearby. Simple runs means you can use a low static unit as well.
If you don't want to loose ceiling height, you can always bump up the overall ceiling on the 2nd floor to 9', nobody ever complains about having taller bedrooms. Another option is to order plenum trusses.
Hi Akos,
问题是图纸已经由工程师盖章。是否仍然可以使用隐藏单元并将管道运到2x4墙壁？
Thank you,
Arnold
If your joists are dimensional lumber, the only way to run ducts perpendicular to the joists is in a bulkhead.
查看您的计划，在公用事业/loudery室的设备中，您可以穿过房子，但是您无法到达没有舱壁的寄存器。一种选择是沿着一室房间，化妆间和走廊在舱壁上运行供应躯干。在那里形成几个顶级起飞罐，而不是沿着地板托梁的跑步供应每个寄存器。
如果生活和厨房之间的LVL齐平并不吼托，您必须找到另一个客厅供应的位置。
The 2nd floor is a bit more challenging, you can run 3 1/4x14 ducts inside 2x4 walls as long as you can get a feed to these from the bottom. The bigger issue is that you need a return on the 2nd floor (without a 2nd floor return cooling will suffer) which would be hard to run from the main.
A simpler option might be is to vertical mount the unit in the back of the linen closet on the 2nd floor.
Have a supply trunk in a bulkhead running along the top of the linen closet, just above but inside the bathroom and office door to feed the rest of the rooms.
其余的管道可以在门上方和楼梯间上方的几个小舱壁上再次运行。通常，在A上方但门内的任何舱壁在视觉上都不明显。如果您不想要舱壁，请将您的一些内墙撞到公寓上的双2x4，并在其内部运行管道。
最好的方法是在CAD上全部绘制所有内容，节省大量现场构想，最终您的安装更加干净，更有效。
查看附件，建造更好的NW负载工具绝缘默认设置为
" 2x4 poorly insulated"
...which doesn't correlate very well with the described
"...a two story, slab on grade house with the follow value; slab: R-32, wall: R-60, ceiling: R-90 and ACH: 0.6...."
垃圾IN =垃圾。
If the better than code house description is correct the loads are likely to be less than half what the tool is spitting out.
嗨，达娜，
I couldn't change the default wall assembly since their drop down menu did not work but I ended up changing the default setting manually.
您应该看到手动J暖通设计师发送me using Wrigthsoft Right-Suite Universal 2019 software. It is full of mistake with a heat load of 36,000 BTU/h for my house design. I am in the process of trying to get them to fix their mistake but it is proving to not be easy.
Arnold
>“…看到手动J暖通设计师发给我ing Wrigthsoft Right-Suite Universal 2019 software. It is full of mistake with a heat load of 36,000 BTU/h for my house design. I am in the process of trying to get them to fix their mistake but it is proving to not be easy."
HVAC designers have a strong bias to the conservative (in contravention of instructions found in the Manual-J itself), and VERY few of them are capable of calculating U-factors for non-standard higher performance assemblies such as R60 walls. The better ones will try to guess which other assembly in the tool's menu seems most comparable to them, but there really isn't anything anywhere near close to R60 walls in most tools' menus. This is the sort of thing best left to actual engineers and performance building modelers.
嗨，达娜，
>“…This is the sort of thing best left to actual engineers and performance building modelers."
感谢您的回答Dana，这就是我目前所结束的。
It's been a bit of a waste of money for me and I still don't have an accurate Manual J to submit with my building permit or to provide the HVAC contractor.
You wouldn't happen to be looking for some work by any chance Dana?
Thank you,
Arnold
Given how common errors are, standard advice needs to be to provide the load results AND all of the inputs (so one can verify them).
On other hand, a 6K overestimate on a 30K 1:1 mini-split load only has a significant effect if it forces much more expensive equipment (it typically doesn't).
Hi Jon,
我得到的是30k BTU的负载，但是我在HVAC中并不是很知识，因此如果真正的负载接近25k，我不会惊讶，因为这里的建议是被动的房屋建造者。
Thank you,
Arnold
No matter what there are built in assumptions and estimations in all models that cannot be mathematically eliminated. Good luck with "actual engineers", some are more "actual" than others and it might be hard to tell which is which since most will likely claim to be.
值得庆幸的是，这些系统有些灵活，这显然是朝着未来和远离中央热量/空气的转变，在我看来，这一技术确实落后了40年，并且在这一点上正在消失。
Is it better to go with two ceiling concealed unit, one for each floor for zoning or one Multi-Position air handling unit for the entire house?
All of these would be installed in the utility room.
谢谢，
Arnold