INSULATED LOG HOMES
A log for a log home has a plurality of pockets formed within the body of the log. The pockets are filled with foam to enhance the thermal rating of the log.
This application is a continuation of U.S. patent application Ser. No. 12/491,561 filed on Jun. 25, 2009; which claims priority from Canadian Patent Application No. 2,633,134 filed on Jun. 25, 2008 and U.S. Provisional Patent Application No. 61/090,757 filed on Aug. 21, 2008, the contents of which are incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to logs for use in log homes.
SUMMARY OF THE INVENTIONIt is well known to utilize logs stacked one above another to form the wall of a house. The intersection of logs at corners is accommodated through overlapping joints, either a saddle splined joint or a dovetail joint by providing a connection to a post. Such construction provides an aesthetically pleasing finished product and reflects the traditional values of the environment in which such houses are typically built. Such houses are formed from logs that are rough hewn to shape as they are built into a wall and the gap between the logs sealed with “chinking”. As an alternative to the hand hewn log homes, machined logs have been utilized in the construction. Machined logs have a uniform cross section and the abutting faces of the logs are machined to form a seal system to inhibit the ingress of air between the logs making up the wall. Such construction offers greater thermal efficiency for the building and assists in meeting the air infiltration standards of the relevant building codes.
A further aspect of the building code is the minimum thermal rating, commonly referred to as the R value in North America or U-value ate Europe, which is the reciprocal of the R value of the wall. U=5.682/R, taking into account the change in units. The R value for a log is accepted to be R 1.25 per inch and to meet a requirement for a minimum insulation value of R16 it would be necessary to provide 12 inch thick logs. Logs of this dimension are expensive and difficult to obtain in volume and as such make it difficult to attain the minimum values required. It is of course possible to increase the thermal efficiency by insulating the internal surface of the wall but this detracts from the inherent aesthetic value of the log wall construction.
A number of attempts have been made to increase the thermal rating of the log wall material by implementing a thermal break in the log. One of those is shown in PCT application WO 96/07802 in which a plurality of longitudinal slots are cut into the body of the log so as to attempt to provide the necessary thermal efficiency. It is then suggested that thin foam strips can then be set into those cuts. However such an arrangement destroys the integrity of the log and requires careful manufacture in order to ensure that the natural movement of the wood does not result in degradation of the log itself. The logs are invariably machined in a green state and dry over a period of time after assembly. The machining of relatively thin sections leads to the cupping and warping of the sections so that an irregular section of the log is obtained.
Moreover, such an arrangement also makes it difficult for the inter-engaging seal profiles to be manufactured and maintained. The inter engaging profiles are tapered so as to obtain a close fit between the adjacent logs. The sealing material placed between the logs is then compressed as the logs are brought together. Because of the natural movement of the material of the log, an effective seal can only be obtained if the two logs are forced into contact and subsequently held with the seal in a compressed state. This is typically done by using bolts that extend vertically through the wall and tightened to hold the logs together. The bolts may be periodically tightened as the house dries to maintain the compressive load. The tapered profile of the sealing area therefore generates a significant lateral load when the logs are assembled in to a wall that must be resisted if the seal is to remain effective and ingress of air is to be avoided. A log formed by a series of laminar sections does not have the necessary lateral strength to resist the lateral loads imposed and would therefore not offer a practical solution.
Even if those deficiencies are ignored, practically it is not possible to insert or place foam within a narrow slot of the nature described in the above application. Rigid foam cannot be inserted due to the friction occurring between the foam and the sides of the slot, and if a clearance is provided to make this possible a loose fit of the foam is obtained. If the foam is injected, the narrow slots cause the foam to bridge and therefore mi fully fill the slots. The force of the expansion is also likely to increase the lateral loading on the thin sections, causing further misalignment and deviation.
Norwegian patent application 173068 similarly describes a log arrangement with thin elongate slots and sections of log and so is subject to the same deficiencies.
Similar deficiencies exist with the arrangements shown in U.S. Pat. Nos. 4,344,263 and 3,992,838. Both of these proposals require a continuous slot filled with foam and extending partially through the log. As such both are susceptible to capping of the sections of the log and movement in a lateral direction. The Farmont proposal addresses this issue with a metal strap across the groove but this not only increases the cost of the manufacture, it also makes it impractical to adopt the sealing profiles necessary to obtain the air tight seal between logs.
It has also been proposed to laminate a log construction to obtain a thermal break by using inner and outer log panels with a plastic foam block between as shown in WO/95/30807. Such a process, however, is very expensive to produce and has the risk of de-lamination between the foam and the exterior panels given the lifecycle of such a building. De-lamination would subject the foam core to crushing due to the weight of the balance of the logs and as such is not an acceptable practice. The foam would not offer the requisite lateral strength for sealing between the logs.
There is therefore the need for a log construction in which the thermal rating of the log may be increased without destroying the structural integrity of the log.
In general terms the present invention provides a log having a plurality of pockets formed at spaced locations along the log. The pockets are separated by lands constituted by the material of the log that extend transversely between oppositely directed faces of the log. The pockets are filled with an insulating material, typically a foam. The lands are dimensioned to provide sufficient lateral rigidity to withstand forces imposed and maintain the structural integrity of the log.
By providing discreet pockets along the length of the log, the structural integrity of the log is maintained whilst its thermal rating is increased. Sealing profiles may be machined on each of the sealing faces and the terminal portions of the log may be devoid of pockets to permit normal joint construction for the corners.
In one embodiment, the pockets are blind bores extending from an upwardly directed surface of the log and terminating prior to the lower surface. In another embodiment, the bores extend through the log and in a further embodiment the pockets are tapered to receive a tapered plug of pre-foamed foam. Generally the bores are perpendicular to the log surfaces but they may be inclined to increase the cross sectional area if preferred. In a further embodiment, the bores extend between opposed faces of the log so when the logs are stacked, the bores are aligned and provide a continuous column of foam.
Embodiments of the invention will now be describing by way of example only with reference to the accompanying drawings in which,
Referring therefore to the drawings, in
Each of the walls 12, 14 is formed from a plurality of logs 20 that extend horizontally and are stacked one above another in a vertical direction. As can be seen in
The log 20 is shown in greater detail in
The body portion 40 is formed with a plurality of pockets each defined by bores 46 that extend from the upper surface 26 toward the lower surface 28. In the embodiment of
The bore 46 is filled with a expanded foam plug 50 that extends up to the upper surface 26 and is formed to have the same profile as the upper surface 26, as will be described below. The foam plug 50 is typically a closed cell foam such as urethane having a high thermal insulation value. Typically such foams have an insulation of R6 per inch and a suitable foam is available from Polyurethane Foam Systems Inc. of Waterloo, Ontario under the trade name Polarfoam PF-6352-0.
The foam plug 50 may be formed in situ using the bore 46 as a mould. In this case, the lower face of the bore 46 provides a closed vessel to permit pouring of the liquid foam.
With the configuration of pockets shown in
The provision of the bores 46 is also beneficial to the production of the logs 20. By pre-drilling the logs 20 with the bores 46 they may be stored upside down to prevent water collecting in the bores 46. The provision of the bores 46 decreases the drying time of the log 20 significantly from the typical twelve months, allowing the inventory of log 20 to be reduced. Moreover the whole structure also has the effect of stress relieving the log 20 and thereby reducing the surface cracking that is typically present on the surfaces 22, 24. Such surface tracking does not reduce the overall strength of the log 20 but it is aesthetically displeasing. The cracking that does occur will take place on the upper surface 26 between the pockets, thereby enhancing the thermal efficiency of the lands 48 without adversely affecting the structural strength.
The logs 20 as shown in the embodiments of
It will be appreciated that the extent of the body 40 may vary from log to log to accommodate features of the building 10 such as doorways and windows. It that event, the end portions 42 may be left solid to accommodate joints or other fixtures, but logs extending across such openings can have the foam plugs 50. The configuration of the bores 46 may vary according to different requirements. For example, in
In general terms, the lands 48 have a dimension along the longitudinal axis of the log, referred to as the thickness of the land, that is sufficient to withstand the lateral forces imposed on the log. The lands 48 provide a continuous web between the boundary layers 49, which, when combined with the dimensions of the bores 46, inhibit spreading of the inner and outer surfaces 22,24. Typically, the thickness of the land 48 is greater than the minimum boundary layer 49. The thickness of the land 49 is also less than the longitudinal dimension of the bore 46. Preferably, the bores 46 have an aspect ratio, that is the ratio of the longitudinal dimension to the lateral dimension, that is not greater than 2:1 so that the lateral or transverse dimension of the bore 46 is at least 50% of the longitudinal dimension. The dimensions may be adjusted to suit the logs involved and attain the average thermal rating required by the building code.
The bores 46 may also be manufactured with varying cross sections as shown in
In the embodiment of
As shown an Table 1 below, a number of different configurations may be used to obtain the desired increase in R-value with relatively few pockets. In the first configuration shown in row 1, circular bores of 3 inch radius extend through the log and are spaced apart by a land of 21.5 inch. Surprisingly, the R value of the log is increased from 10.4 to 16.3, which is sufficient to meet the Canadian budding code requirements. This increase is attained with a relatively small number of pockets which maintains the integrity of the log.
Similar results are shown in row 2 where square pockets are spaced apart 24 inches to get a similar increase in R value. With overlapping circular bores of 3 inch diameter, as shown in row 3, a land of 3S inches may be used and with an elongated oval, as shown in row 4, a spacing of 45 inches is possible whilst maintaining an R-value above 16.
An array of smaller diameter staggered pockets, as shown in row 5, may also be used to attain the required value.
From the above, it will be seen that a variety of configurations may be adopted to obtain the requisite thermal rating, and that where a particular rating is required, the ratio of foam filled pockets to original log may be adjusted to provide this. As shown below in Table 2, reducing the pocket cross section and the spacing enables the same thermal rating to be achieved as the equivalent configuration in table A, thereby illustrating the versatility of the arrangement when meeting particular building requirements, such as interconnecting walls and services.
In each of the above embodiments, the bore 46 is of uniform cross section and terminates prior to the lower surface 28. The bores 46 may of course extend through the log, provided provision is made for inserting the foam. When the bore extends fully through the log, as illustrated in
It will also be appreciated that the cross sectional area of the bore 46 may be increased by inclining the axis of the bore 46. In the embodiment shown in
In an alternative arrangement as shown in
It will be appreciated of course that the arrangement shown in
To facilitate insertion of preformed plugs, the arrangement shown in
The portions 50a, 50b are held in situ by a wedging action in the gap 60. In one embodiment, the gap 60 is filled with expandable foam which expands to hold the portions 50a, 50b, and the relatively small gap enables the foam to be supplied by pressurised containers if on site installation is required.
It will be seen therefore that the provision of the pockets in the log 20 provides an opportunity to increase the thermal rating without adversely affecting the integrity of the log. The lands between each of the bores ensure that the inner and outer faces are secured at all times to one another and also provides sufficient strength to avoid crushing of the log. The provision of the foam also allows the sealed profiles to be machined in the plug together with the balance of the sealing faces and for the log to maintain the integrity of the end portions for conventional joining techniques.
A further embodiment of log is shown in
The upper surface 26a and lower surface 20a are configured to provide opposed, abutting ledges 70 and an internal cavity 72 when the logs 20a are assembled. One of the ledges 70, on the lower surface 28a in the embodiment of
The cavity 72 is formed between the ledges 70 in the centre portion of the upper surface 26a and lower surface 28a. The upper surface 26a is formed with an upstanding shoulder 78 inboard of the ledges 70 and a recessed channel 80 that extends downwardly to intersect the foam plug 50a.
The lower surface 28 is similarly formed with a central recess 82 that extends to the plug 50a and is spaced from the shoulders 78.
It will be appreciated that the shoulders 78, channel 80 and recess 82 extend the length of the log as a uniform cross section and may terminate prior to the end sections to allow the conventional joint to be manufactured.
A series of lateral holes 84 are machined from one side of the log 20a so as to intersect the channel 80 at regular intervals. The holes 84 are spaced along the length of the log and are of sufficient diameter to allow a foaming wand to be inserted into the hole 84.
To assemble a wall using the embodiment of
The foam utilized in the preferred embodiment is a foamed polyurethane product such as the that sold under the name “Insulator” available from NCFI Polyurethanes of Airy N.C. and provides adherence to the wood of the log 20a to inhibit separation of the logs 20a. The preferred foam is a two component, one to one by volume self adhering seamless high efficiency rigid polyurethane foam adhesive system. The product identified as NCFI 11-018 has been found suitable. The foam provides insulative properties and adheres to the logs 20a to connect the two opposed faced. The foam injected into the channel 72 therefore not only acts as a thermal insulation between the logs 20a but also acts to secure the logs 20a to one another to provide an integral wall. Separation of the logs 20a as they dry is therefore inhibited and ingress of air between the logs 20a inhibited.
The building may be assembled in a conventional manner by stacking the logs 20a one above the other with the shoulders 78 locating the logs laterally. Tie bolts may be inserted through the logs in a conventional manner to provide an initial setting of the logs 20a.
Once assembled, the foam is then injected into the cavity 72 to fill the cavity and secure the logs to one another.
Once foamed, the plugs are inserted and the building may be finished. Thereafter, the relative movement between adjacent logs 20a due to changes in humidity is inhibited by the adhesion of the foam with the cavity.
Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto. The entire disclosures of all references recited above are incorporated herein by reference.
Claims
1) A log having an elongate body with a pair of oppositely directed wall faces extending between a pair of oppositely directed sealing faces, a plurality of pockets extending from one of said sealing faces through said body to the other of said sealing faces, said pockets being uniformly spaced along said body, said pockets being separated from one another by lands extending between said wall faces—said pockets and lands being dimensioned relative to one another to preserve structural integrity of said log and maintain relative spacing of said wall faces.
2) A log according to claim 1 wherein terminal portions of said body are devoid of pockets.
3) A log according to claim 1 or 2 wherein said sealing face has sealing formations formed thereon for engagement with a complimentary formation on an adjacent log.
4) A log according to any one of claims 1 to 3 wherein said land between pockets has a dimension measured along the longitudinal axis less than the corresponding dimension of said pocket but greater than the spacing of said wall faces from a periphery of said pocket.
5) A log according to any one of claims 1 to 4 wherein said pockets are of substantially constant cross section.
6) A log according to any one of claims 1 to 4 wherein said pockets taper.
7) A log according to any one of claims 1 to 6 wherein said pockets are distributed and sized to provide an increased in thermal rating of said log to at least R16, when said pockets are filled with foam.
8) A log according to any one of claims 1 to 7 wherein said pockets are filled with foam.
9) A log according to claim 8 wherein said foam is preformed and inserted in to said pockets as plugs.
10) A log according to claim 9 wherein a pair of plugs is inserted in a pocket and retained by a wedge spreading said plugs.
11) A log according to claim 9 wherein said plug and pocket are tapered and said plug is retained by interference between said pocket and said plug.
12) A log according to any one of claims 1 to 11 wherein said pocket has a dimension between said wall faces of 50% of the spacing between said wall faces.
13) A log according to any one of claims 1 to 12 wherein said pockets are circular.
14) A log according to any one of claims 1 to 12 wherein said pockets are square.
15) A log according to any one of claims 1 to 12 wherein said pockets are oval.
16) A building including at least one log according to any one of claims 1 to 16.
17) A building according to claim 16 wherein intersecting walls of said building are formed with logs according to any one of claims 1 to 16 and wherein terminal portions of said logs are devoid of pockets.
18) A building according to claim 17 wherein said terminal portions are formed as interlocking joints.
19) A method of forming a log having a pair of oppositely directed sealing faces, said method comprising the steps of forming a plurality of pockets in said log at uniformly spaced intervals along said body, said pockets extending from one of said sealing faces through said log to the other of said sealing faces said pockets being spaced apart greater than the dimension of said pocket along the axis of said long to provide a land extending between said pockets and filling said pockets with insulating foam.
20) A method according to claim 19 including the step of machining formations on said one face after said foam is formed in said pockets.
21) A method according to claim 19 or 20 wherein said foam is preformed and inserted in to said bores.
22) A method according to claim 21 wherein said pocket is tapered and said foam is preformed with a complementary taper.
23) A method according to claim 21 where said foam is inserted in said pocket as a pair of portions and retained in said pocket by a wedge acting between said portions.
24) A method according to claim 23 wherein said wedge is a foam inserted between said portions.
25) A log having an elongate body with a pair of oppositely directed wall faces extending between a pair of oppositely directed sealing faces, a plurality of pockets extending from one of said sealing faces into said body and uniformly spaced along said body, said pockets being separated from one another by lands extending continuously between said wall faces each of said pockets having a dimension measured in a direction transverse of said walls that is not less than 50% of the spacing between said walls, said pockets and lands being dimensioned relative to one another to preserve the structural integrity of said log and to maintain relative spacing of said wall faces.
26) A log according to claim 25 wherein said lands have a dimension measured along the longitudinal axis of said log less than the corresponding dimension of said pocket but greater than the spacing of said wall faces from a periphery of said pocket.
27) A log according to claim 25 or 26 wherein said pockets haven combined volume that is at least 20% of the volume of said log.
28) A log according to any one of claims 25 to 27 wherein said pockets have a transverse dimension at least 50% of the longitudinal dimension.
29) A log according to any one of claims 25 to 28 wherein said sealing face has sealing formations formed thereon for engagement with a complimentary formation on an adjacent log.
30) A log according to any one of claims 25 to 29 wherein said pockets extend between said sealing faces.
31) A log according to any one of claims 25 to 30 wherein said pockets are of substantially constant cross section.
32) A log according to any one of claims 25 to 30 wherein said pockets taper.
33) A log according to any one of claims 25 to 32 wherein said pockets are distributed and sized to provide an increased thermal rating of said log to at least R16 when said pockets are filled with foam.
34) A log according to any one of claims 25 to 33 wherein said pockets are filled with foam.
35) A log according to claim 34 wherein said foam is preformed and inserted in to said pockets as plugs.
36) A log according to claim 35 wherein a pair of plugs is inserted in a pocket and retained by a wedge spreading said plugs.
37) A log according to claim 35 wherein said plug and pocket are tapered and said plug is retained by interference between said pocket and said plug.
38) A log according to any one of claims 25 to 37 wherein terminal portions of said body are devoid of pockets.
39) A log according to any one of claims 25 to 38 wherein said pockets are circular.
40) A log according to any one of claims 25 to 38 wherein said pockets are square.
41) A log according to any one of claims 25 to 38 wherein said pockets are oval.
42) A building including at least one log according to any one of claims 25 to 41.
43) A building according to claim 42 wherein intersecting walls of said building are formed with logs according to any one of claims 25 to 41 and wherein terminal portions of said logs are devoid of pockets.
44) A building according to claim 43 wherein said terminal portions are formed as interlocking joints.
45) A method of forming a log having a pair of oppositely directed sealing faces and a pair of oppositely directed wall faces, said method comprising the steps of forming a plurality of pockets in said log to extend not less than 50% of the distance between said wall faces and extending from one of said sealing faces to the other of said sealing faces with a land extending between said pockets and filling said pockets with insulating foam.
46) A method according to claim 45 wherein said foam is formed in situ.
47) A method according to any one of claims 45 or 46 including the step of machining formations on one of said sealing faces after said foam is formed in said pockets.
48) A method according to claim 45 wherein said foam is preformed and inserted in to said bores.
49) A method according to claim 48 wherein said pocket is tapered and said foam is preformed with a compounding taper.
50) A method according to claim 48 where said foam is inserted in said pocket as a pair of portions and retained in said pocket by a wedge acting between said portions.
51) A method according to claim 50 wherein said wedge is a foam inserted between said portions.
52) A method of forming a wall of a log building by stacking logs vertically one above another with abutting faces cooperating to define an internal cavity and injecting a foam within said cavity after assembly of said logs to connect said logs to one another.
53) A method according to claim 52 wherein pockets are formed in said logs extending from one of said abutting faces prior to assembly of said logs into a wall.
54) A method according to claim 53 wherein foam is inserted in said pockets prior to assembly of said logs into a wall.
Type: Application
Filed: Oct 31, 2012
Publication Date: Jul 25, 2013
Inventor: Ronald A. WRIGHTMAN (Bracebridge)
Application Number: 13/665,336
International Classification: E04B 2/70 (20060101);