Electric hydronic radiant heat
大家好，
我正在为我的母亲设计一间小屋，该小屋将于明年夏天在佛蒙特州中部建造。它是20'x 34'单层，可能是棚屋（南方曝光高16'，北部暴露于12'）。Wall assembly isn’t totally hammered down yet, but likely 2×6 walls with cellulose in cavity and rigid foam on exterior, lots of cellulose in the roof, and careful air sealing throughout (the envelope is very simple in order to make air sealing easier). Goal for R values will be 30-40 in walls and 60 in roof.
我的问题是要加热建筑物。我在自己的房子里安装了带有无油箱加热器的辐射地板，我真的很喜欢它，并希望为她做同样的事情。但是我也有兴趣将所有公用事业电动保持电动，因此我们可以通过添加一个小的PV阵列来达到净零。我知道我只能使用一个热泵，但由于几个原因，我真的不喜欢它们 - 我不喜欢吹气，而且我不喜欢在房子外面有一个丑陋的压缩机。因此，我的问题是：使用电热水器加热水力地板是否疯狂？我的感觉是，在这座相当高性能标准的建筑物中，它可能会很好。
Please note this question is about using an electric water heater for radiant, not so much about the pros and cons of radiant heat. I know it’s not for everyone, slow to respond, etc., but I really like it.
非常感谢，
山姆
GBA Detail Library
由气候和房屋部分组织的一千个建筑细节的集合
答复
电动辐射可能会便宜地安装。用电热源的水电的唯一优点是将来更换热源的选择。
辐射的热量很好，很可能会加热小屋，但是在空调和除湿的空调和除湿中很糟糕，这对老年人来说很重要，而且非常重要。我已经建造了几个房屋，我的客户不想要丑陋的墙单元（Minisplits），但是在看到行动中的单元后，改变了主意，也没有后悔。数十年来，我们在家里有“热空气”的热量，几年前升级为Minisplits - 没有比较。迷你的使用非常低的风扇设置；它们是安静且不引人注目的，并且是迄今为止我使用过的最好的供暖源。但是，如果您只是担心热量而不是舒适，那么您的计划应该可以正常工作。
A shed roof pitch facing north means no rooftop solar. Is that "...small PV array..." going to be ground mounted?
电热水器是用于用途的电动锅炉的非常crump的替代品。电动锅炉的尺寸范围很大，几乎适合任何热负荷。在宏伟的情况下，可以使用低2kw的锅炉，并且与电热水器不同，它是为辐射地板所需的税收周期和流动而设计的。
Choosing the heating system before running the heat load numbers is folly.
The perfomance goals of "...R values will be 30-40 in walls and 60 in roof..." are extremely ill-defined, unless you're talking about "whole-assembly R", that calculates all there thermal bridging in the framing, the R-values of sheathing, siding, gypsum board, roofing, etc. Five inches of HFO blown 2lb foam in a 2x6 studwall 16" on center is about R35 at center-cavity, but would result in a whole-wall R of less than R20. A 2x4/R13 wall with 3" of continuous polyiso sheathing would be only R31, but would have a whole -wall R in the R28-R30 range.
Hi Dana
Just came across your comments from 2018. I have the same questions as the OP. Can you provide more info about electric boilers? Specific questions are typical longevity, maintenance, and would you couple the boiler with an indirect water heater for domestic hot water?
您还可以评论计算热负荷吗？这是我自己可以做的事情吗？您推荐有在线计算器吗？
区域3C
Thank you
>"Can you also comment on calculating heat loads? Is this something I can do myself? Are there online calculators you recommend?"
If you lived in a colder climate and had a heating history you could get reasonably accurate results for load using energy use against heating degree-day data. But zone 3C it's so temperate the results would be skewed by solar gain, water use, and negative HDD days in any given billing period. Though it will probably deliver paradoxical results in your climate zone, that method looks like this:
greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new
That leaves you with Manual-J or similar:
https://www.coolcalc.com/
https://loadcalc.net/
...or... an I=B=R method approach:
//m.etiketa4.com/article/how-to-perform-a-heat-loss-calculation-part-1
//m.etiketa4.com/article/how-to-perform-a-heat-loss-calculation-part-2
Even when using the most aggressive assumptions on air tightness LoadCalc tends to overshoot by 20% or more, and will overshoot by a LOT if all of your inputs err to the conservative rather than aggressive/optimistic. CoolCalc is an ACCA registered Manual-J tool, but like all calculators garbage in= garbage out. The instructions in the ACCA Manual-J specify that all factors that could potentially reduce the load number need to be factored in for it to be reasonably accurate, so be aggressive/optimistic on all R-value, U-factor, and air tightness assumptions.
>“您能提供有关电动锅炉的更多信息吗？具体的问题是典型的寿命，维护，您是否可以将锅炉和间接热水器与家用热水搭配使用？”
在3C区域中，热泵热水器比用电动锅炉间接的效率要高得多。即使是普通的旧电罐也会更有效。
Electric boilers are pretty rugged, and don't need much in the way of maintenance. As long as the systems water isn't too acid (check the pH every year or three) and it isn't being crazy over-pumped (or drastically underpumped) it should last for decades at the kind of duty cycle you'd see in zone 3C.
谢谢！
如果您的负载相对较低，则与辐射热水绑在一起的砂hwh是一个很好的有效解决方案。我现在正在寻找Sanden Heat+DHW，以及用于冷却，除湿，通风和补充热量的Minotair。
A Chiltrix air to water heat pump is another option. You can use it with both a radiant floor (Winter) and fan coils (Summer AC).
任何带有水箱的东西都将允许一些时间转移用电。这将变得越来越重要（对于$和环境）。