"U-value" meaning in English

{
  "forms": [
    {
      "form": "U-values",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "U-value (plural U-values)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "thermal transmittance or thermal conductance"
      ],
      "id": "en-U-value-en-noun-XTO6Cx2n",
      "links": [
        [
          "thermal transmittance",
          "thermal transmittance"
        ],
        [
          "thermal conductance",
          "thermal conductance"
        ]
      ]
    }
  ],
  "word": "U-value"
}

{
  "forms": [
    {
      "form": "U-values",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "U-value (plural U-values)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns"
      ],
      "glosses": [
        "thermal transmittance or thermal conductance"
      ],
      "links": [
        [
          "thermal transmittance",
          "thermal transmittance"
        ],
        [
          "thermal conductance",
          "thermal conductance"
        ]
      ]
    }
  ],
  "word": "U-value"
}